s that all forms of life
originally commenced as _Monera_, or simple particles of protoplasm;
and that these _Monera_ originated from not-living matter. Some of the
_Monera_ acquired tendencies towards the Protistic, others towards the
Vegetal, and others towards the Animal modes of life. The last became
animal _Monera_. Some of the animal _Monera_ acquired a nucleus, and
became amoeba-like creatures; and, out of certain of these, ciliated
infusorium-like animals were developed. These became modified into two
stirpes: A, that of the worms; and B, that of the sponges. The latter
by progressive modification gave rise to all the _Coelenterata_; the
former to all other animals. But A soon broke up into two principal
stirpes, of which one, _a_, became the root of the _Annelida,
Echinodermata_, and _Arthropoda_, while the other, _b_, gave rise to
the _Polyzoa_ and _Ascidioida_, and produced the two remaining stirpes
of the _Vertebrata_ and the _Mollusca_.

Perhaps the most startling proposition of all those which Professor
Haeckel puts before us is that which he bases upon Kowalewsky's
researches into the development of _Amphioxus_ and of the
_Ascidioida_, that the origin of the _Vertebrata_ is to be sought
in an Ascidioid form. Goodsir long ago insisted upon the resemblance
between _Amphioxus_ and the Ascidians; but the notion of a genetic
connection between the two, and especially the identification of the
notochord of the _Vertebrate_ with the axis of the caudal appendage of
the larva of the Ascidian, is a novelty which, at first, takes one's
breath away. I must confess, however, that the more I have pondered
over it, the more grounds appear in its favour, though I am not
convinced that there is any real parallelism between the mode
of development of the ganglion of the _Ascidian_ and that of the
_Vertebrate_ cerebro-spinal axis.

The hardly less startling hypothesis that the _Echinoderms_ are
coalesced worms, on the other hand, appears to be open to serious
objection. As a matter of anatomy, it does not seem to me to
correspond with fact; for there is no worm with a calcareous skeleton,
nor any which has a band-like ventral nerve, superficial to which lies
an ambulacral vessel. And, as a question of development, the formation
of the radiate _Echinoderm_ within its vermiform larva seems to me
to be analogous to the formation of a radiate Medusa upon a Hydrozoic
stock. But a Medusa is surely not the result of the coalesce