cally
extinct, as we now use the word. Lamarck in theory was throughout, as
Houssay well says, at one with us who are now living, but a century
behind us in knowledge of the facts needed to support his theory.

In this first published expression of his views on palaeontology, we find
the following truths enumerated on which the science is based: (1) The
great length of geological time; (2) The continuous existence of animal
life all through the different geological periods without sudden total
extinctions and as sudden recreations of new assemblages; (3) The
physical environment remaining practically the same throughout in
general, but with (4) continual gradual but not catastrophic changes in
the relative distribution of land and sea and other modifications in the
physical geography, changes which (5) caused corresponding changes in
the habitat, and (6) consequently in the habits of the living beings; so
that there has been all through geological history a slow modification
of life-forms.

Thus Lamarck's idea of creation is _evolutional_ rather than
_uniformitarian_. There was, from his point of view, not simply a
uniform march along a dead level, but a progression, a change from the
lower or generalized to the higher or specialized--an evolution or
unfolding of organic life. In his effort to disprove catastrophism he
failed to clearly see that species, as we style them, became extinct,
though really the changes in the species practically amounted to
extinctions of the earlier species as such. The little that was known
to Lamarck at the time he wrote, prevented his knowing that species
became extinct, as we say, or recognizing the fact that while some
species, genera, and even orders may rise, culminate, and die, others
are modified, while a few persist from one period to another. He did,
however, see clearly that, taking plant and animal life as a whole, it
underwent a slow modification, the later forms being the descendants of
the earlier; and this truth is the central one of modern palaeontology.

Lamarck's first memoir on fossil shells, in which he described many new
species, was published in 1802, after the appearance of his
_Hydrogeologie_, to which he refers. It was the first of a series of
descriptive papers, which appeared at intervals from 1802 to 1806. He
does not fail to open the series of memoirs with some general remarks,
which prove his broad, philosophic spirit, that characterizing the
founder of a n