fficulties here discussed, namely, that, though we find in
our geological formations many links between the species which now exist
and which formerly existed, we do not find infinitely numerous fine
transitional forms closely joining them all together. The sudden
manner in which several groups of species first appear in our European
formations, the almost entire absence, as at present known, of
formations rich in fossils beneath the Cambrian strata, are all
undoubtedly of the most serious nature. We see this in the fact that
the most eminent palaeontologists, namely, Cuvier, Agassiz, Barrande,
Pictet, Falconer, E. Forbes, etc., and all our greatest geologists, as
Lyell, Murchison, Sedgwick, etc., have unanimously, often vehemently,
maintained the immutability of species. But Sir Charles Lyell now
gives the support of his high authority to the opposite side, and most
geologists and palaeontologists are much shaken in their former belief.
Those who believe that the geological record is in any degree perfect,
will undoubtedly at once reject my theory. For my part, following out
Lyell's metaphor, I look at the geological record as a history of
the world imperfectly kept and written in a changing dialect. Of this
history we possess the last volume alone, relating only to two or three
countries. Of this volume, only here and there a short chapter has been
preserved, and of each page, only here and there a few lines. Each
word of the slowly-changing language, more or less different in the
successive chapters, may represent the forms of life, which are entombed
in our consecutive formations, and which falsely appear to have been
abruptly introduced. On this view the difficulties above discussed are
greatly diminished or even disappear.

CHAPTER XI. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS.

On the slow and successive appearance of new species--On their different
rates of change--Species once lost do not reappear--Groups of species
follow the same general rules in their appearance and disappearance as
do single species--On extinction--On simultaneous changes in the forms
of life throughout the world--On the affinities of extinct species to
each other and to living species--On the state of development of
ancient forms--On the succession of the same types within the same
areas--Summary of preceding and present chapters.

Let us now see whether the several facts and laws relating to the
geological successio