the botanical system. The same thing is true in the animal
kingdom. If the eozoon Canadense, found in the laurentian slate of the
Cambrian formation in North America, is really an organism and not an
inorganic form, the earliest vestiges of animal life we can find are the
rhizopodes or foraminifera; and these organisms belong to the lowest stage
of life--to that stage which forms a kind of undeveloped intermediate
member between the vegetable and animal kingdom, Haeckel's kingdom of the
protista. The next oldest animal organisms found in the Cambrian formation
are the zooephytes, and immediately above them the mollusca and the
crustacea. In the following Silurian period we find corals, radiata, worms,
mollusca, and crustacea, in {66} great number, also all the main-types of
the invertebrates; and in the highest Silurian strata there are also to be
found representatives of the lowest class of vertebrates, of fish, but
still of very low organization and little differentiated. That the five
main-types of the invertebrates seem to have appeared quite
contemporaneously, yet that the zooephytes really appeared first, does not
contradict the before-mentioned law of a progress in the appearance of the
organisms from the lower to the higher. For in the zooelogical system also
these main-types of the invertebrates do not stand one above the other, but
by the side of each other: at most, the radiata, the worms, the mollusca,
and the articulata, take their places above the zooephytes. Only within the
main-types, in the classes, orders, etc., do differences in rank take
effect; and even here, not without exception. What difference in rank, for
instance, is there between an oyster and a cuttle-fish? between a cochineal
and a bee or ant? and yet the first two belong to one and the same
type--the type of mollusca; and the last three to one and the same
class--the class of insects. The vertebrates rank decidedly above the
invertebrates; and in a manner wholly corresponding to this, the
vertebrates also appear after the invertebrates. Just as decidedly as to
their rank, the main classes of the vertebrates do not stand beside, but
above one another: above the fish stand the amphibia, above them the
reptiles, next the birds, and above them the mammalia. To this series of
succession also the geological facts seem to correspond pretty closely;
only long after the fish do the first amphibia and reptilia
appear--although it can not yet be decide