from their obscurity to assume the lordship of the globe.

In earlier years, when some serious hesitation was felt by many to
accept the new doctrine of evolution, a grave difficulty was found in
the circumstance that new types--not merely new species and new genera,
but new orders and even sub-classes--appeared in the geological record
quite suddenly. Was it not a singular coincidence that in ALL cases the
intermediate organisms between one type and another should have wholly
escaped preservation? The difficulty was generally due to an imperfect
acquaintance with the conditions of the problem. The fossil population
of a period is only that fraction of its living population which
happened to be buried in a certain kind of deposit under water of a
certain depth. We shall read later of insects being preserved in resin
(amber), and we have animals (and even bacteria) preserved in trees from
the Coal-forests. Generally speaking, however, the earth has buried only
a very minute fraction of its land-population. Moreover, only a fraction
of the earth's cemeteries have yet been opened. When we further reflect
that the new type of organism, when it first appears, is a small and
local group, we see what the chances are of our finding specimens of
it in a few scattered pages of a very fragmentary record of the earth's
life. We shall see that we have discovered only about ten skeletons
or fragments of skeletons of the men who lived on the earth before the
Neolithic period; a stretch of some hundreds of thousands of years,
recorded in the upper strata of the earth.

Whatever serious difficulty there ever was in this scantiness of
intermediate types is amply met by the fact that every fresh decade of
search in the geological tombs brings some to light. We have seen many
instances of this--the seed-bearing ferns and flower-bearing cycads, for
example, found in the last decade--and will see others. But one of the
most remarkable cases of the kind now claims our attention. The bird was
probably evolved in the late Triassic or early Jurassic. It appears in
abundance, divided into several genera, in the Chalk period. Luckily,
two bird-skeletons have been found in the intermediate period, the
Jurassic, and they are of the intermediate type, between the reptile
and the bird, which the theory of evolution would suggest. But for
the fortunate accident of these two birds being embedded in an ancient
Bavarian mud-layer, which happened to be op