their parents, the offspring of members of these species are still liable
to vary; and the variation may be perpetuated by selection, as a race,
which race, in many cases, presents all the characteristics of a
morphological species. But it is not as yet proved that a race ever
exhibits, when crossed with another race of the same species, those
phaenomena of hybridisation which are exhibited by many species when crossed
with other species. On the 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
phaenomena 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