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_.

Professor Haeckel proposes to break up the vertebrate sub-kingdom,
first, into the two provinces of _Leptocardia_ and _Pachycardia;
Amphioxus_ being in the former, and all other vertebrates in the
latter division. The _Pachycardia_ are then divided into _Monorhina_,
which contains the Cyclostome fishes, distinguished by their single
nasal aperture; and _Amphirhina_, comprising the other _Vertebrata_,
which have two nasal apertures. These are further subdivided into
_Anamnia (Pisces, Dipneusta, Amphibia)_ and _Amniota (Reptilia, Aves,
Mammalia)_. This classification undoubtedly expresses many of the most
important facts in vertebrate structure in a clear and compendious
way; whether it is the best that can he adopted remains to be seen.

With much reason the Lemurs are removed altogether from the
_Primates_, under the name of _Prosimiae_. But I am surprised to
find the _Sirenia_ left in one group with the _Cetacea_, and the
_Plesiosauria_ with the _Ichthyosauria_; the ordinal distinctness of
these having, to my mind, been long since fully established.

V. In Professor Haeckel's speculations on Phylogeny, or the genealogy
of animal forms, there is much that is profoundly interesting, and
his suggestions are always supported by sound knowledge and great
ingenuity. Whether one agrees or disagrees with him, one feels that
he has forced the mind into lines of thought in which it is more
profitable to go wrong than to stand still.

To put his views into a few words, he conceive