nto another, in consequence
merely of the experience of wants calling for the exercise of faculties
in a particular direction, by which exercise new developments of organs
took place, ending in variations sufficient to constitute new species.
In this way the swiftness of the antelope, the claws and teeth of the
lion, the trunk of the elephant, the long neck of the giraffe have been
produced, it is supposed, by a certain plastic character in the
construction of animals, operated upon for a long course of ages by the
attempts which these animals make to attain objects which their previous
organization did not place within their reach. This is what is meant by
the hypothesis of _progressive tendencies_, and which requires for its
validity not only the assumption of a mere capacity for change, but of
active principles conducive to improvement and the attainment of higher
powers and faculties. More recently ST. HILAIRE has published a paper in
which he speaks of the immutability of species as a conviction that is
on the decline, and that the age of CUVIER is on the close. Carried away
by what Professor PHILLIPS has called a poetical conjecture that cannot
be proved, this writer propounded the speculation that the present
crocodiles are really the offspring of crocodilian reptiles, the
difference being merely the effect of physical conditions, especially
operating during long geological periods upon one original race. The
human species, he contends, are but an advanced development of the
higher order of the monkey tribe, and that the negroes are degenerating
towards that type again. According to him the sivatherium--a fossil
animal that had been found in the Himalaya mountains--was the primeval
type that time had fined down into the giraffe from long-continued
feeding on the branches of trees. Dr. FALCONER and Capt. CAUTLEY,
however, have shown that anatomical proofs are all against this
inference, but if any doubt remained it must yield to the fact, that
among the _fauna_ of the Sewalik hills the sivatherium and the giraffe
were contemporaries.

The author of the _Vestiges of Creation_ has put forth an hypothesis
founded on the preceding conjectures, but more compact and conclusive.
He is, as we have seen, in favour of the progressive change of species,
adopting the notion that men once had tails, and that the rudiments of
this condal appendage are found in an undeveloped state in the _os
coccygis_ (p. 199.) His leading idea