la justice de nos theories zoologiques; puisque le
vrai cachet d'une theorie est sans contredit la faculte qu'elle donne de
prevoir les phenomenes."

In the "Ossemens Fossiles" Cuvier leaves his paper just as it first
appeared in the "Annales du Museum," as "a curious monument of the force
of zoological laws and of the use which may be made of them."

Zoological laws truly, but not physiological laws. If one sees a live
dog's head, it is extremely probable that a dog's tail is not far off,
though nobody can say why that sort of head and that sort of tail go
together; what physiological connection there is between the two. So, in
the case of the Montmartre fossil, Cuvier, finding a thorough opossum's
head, concluded that the pelvis also would be like an opossum's. But,
most assuredly, the most advanced physiologist of the present day could
throw no light on the question why these are associated, nor could
pretend to affirm that the existence of the one is necessarily connected
with that of the other. In fact, had it so happened that the pelvis of
the fossil had been originally exposed, while the head lay hidden, the
presence of the "marsupial bones," though very like an opossum's, would
by no means have warranted the prediction that the skull would turn out
to be that of the opossum. It might just as well have been like that of
some other marsupial; or even like that of the totally different
group of Monotremes, of which the only living representatives are the
_Echidna_ and the _Ornithorhynchus._

For all practical purposes, however, the empirical laws of co-ordination
of structures, which are embodied in the generalisations of morphology,
may be confidently trusted, if employed with due caution, to lead to a
just interpretation of fossil remains; or, in other words, we may look
for the verification of the retrospective prophecies which are based
upon them.

And if this be the case, the late advances which have been made in
palaeontological discovery open out a new field for such prophecies. For
it has been ascertained with respect to many groups of animals, that, as
we trace them back in time, their ancestors gradually cease to exhibit
those special modifications which at present characterise the type, and
more nearly embody the general plan of the group to which they belong.

Thus, in the well-known case of the horse, the toes which are suppressed
in the living horse are found to be more and more complete in the o