other hand, not only is it not proved that all species give rise to
hybrids infertile 'inter se', but there is much reason to believe that,
in crossing, species exhibit every gradation from perfect sterility to
perfect fertility.

Such are the most essential characteristics of species. Even were man
not one of them--a member of the same system and subject to the same
laws--the question of their origin, their causal connexion, that is,
with the other phenomena of the universe, must have attracted his
attention, as soon as his intelligence had raised itself above the level
of his daily wants.

Indeed history relates that such was the case, and has embalmed for us
the speculations upon the origin of living beings, which were among the
earliest products of the dawning intellectual activity of man. In
those early days positive knowledge was not to be had, but the craving
after it needed, at all hazards, to be satisfied, and according to the
country, or the turn of thought, of the speculator, the suggestion that
all living things arose from the mud of the Nile, from a primeval egg,
or from some more anthropomorphic agency, afforded a sufficient
resting-place for his curiosity. The myths of Paganism are as dead as
Osiris or Zeus, and the man who should revive them, in opposition to
the knowledge of our time, would be justly laughed to scorn; but the
coeval imaginations current among the rude inhabitants of Palestine,
recorded by writers whose very name and age are admitted by every
scholar to be unknown, have unfortunately not yet shared their fate,
but, even at this day, are regarded by nine-tenths of the civilized
world as the authoritative standard of fact and the criterion of the
justice of scientific conclusions, in all that relates to the origin of
things, and, among them, of species. In this nineteenth century, as at