s gaps which still exist between
these fragmentary documents of former ages are nevertheless too
considerable for continuous connections to be established in the past
by the aid of fossils.

We not only know that the different forms of living beings are
connected to each other by a real relationship, but we can fathom more
and more deeply the degrees of this relationship, and can often prove
from which group of animals a given group is descended. In many cases
we can determine at which period the fauna and flora of two continents
have been separated from each other, and in what manner they have been
transformed, each in its own way, while still preserving the general
characters which were common before their separation. The specialist
can soon discover what species belong to the old geographically
differentiated fauna and flora of the country, and what have been
ulteriorily imported.

I record these facts for the benefit of those persons who have not yet
understood that it is absolutely useless at the present day to dispute
the evolution of living beings. Deceived by the divergent opinions of
scientists concerning hypotheses which endeavor to explain the details
of evolution, these persons confound the details with the fundamental
facts of evolution.

=Ontogeny. Phylogeny.=--In the light of the facts of evolution,
heredity takes quite a new aspect when removed from the old biblical
idea of the independent creation of species. _Haeckel_ launched into
the scientific world, under the name of "fundamental biogenetic law,"
a theory which, without having the right to the title of an immutable
dogma, explains the facts in a general way, and gives us a guiding
line along the phylogenetic history of living beings. "_Ontogeny_,"
that is the history of the embryological development of each
individual, always consists in a summary and fragmentary repetition of
_phylogeny_, or the history of the ancestors of the species to which
the individual belongs. This signifies that, as embryos, we repeat in
an abridged form the series of types or morphological stages through
which has passed the series of our animal ancestors, from the
primitive cell to man. In reality this is only true in a relative way,
for a considerable part of the ancestral engraphias of the embryo has
disappeared without leaving any trace; also many embryos, especially
those which have special conditions of existence outside the body of
their mother, have acquired s