essive
appearance of new species;[4] it reveals to us also that the surface of
the earth has undergone great mutations; that land and sea have frequently
changed places; and that the climate of the several regions of the world,
owing to many causes, has greatly varied. Natural history is replete with
striking accounts of the modifications produced in a race of animals by
the change of climate, diet, and the enforcement of new habits; and
linking all these facts together, it does not appear a very violent
supposition, nor one that departs from the frequent analogies of nature,
to say, that the causes which have brought about the extinction of certain
species may have also operated to the development of new species. The
manifest error of Lamarck was an egregious exaggeration of certain
well-known truths. Because external circumstances may do much in directing
the inherent power of development possessed by a given organization, he
resolved that it should do every thing. The camelopard was to get his long
neck by stretching for his food; and the duck her web-foot by paddling in
the water. But the author before us breaks loose entirely from the region
of facts; or rather he announces to us, on his own responsibility, an
entirely new fact--that it is the law of animal life that each species
should, from time to time, produce a brood of the species next in order of
perfection or complexity of organization. With him, this development is
the result merely of a law of generation which he himself has devised to
meet the emergency.

Amongst the laws of life, the most conspicuous and undoubted is this--that
each species reproduces itself, that like begets like. This law our author
cannot of course gainsay; but he appends to it another overruling law,
that from time to time, at long intervals, the like does not beget the
like, but the different and superior form of organization. In other words,
the old law changes from time to time. Of this novel description of law he
borrows the following illustration of Mr Babbage:--

Unquestionably, what we ordinarily see of nature is calculated to
impress a conviction that each species invariably produces its like.
But I would here call attention to a remarkable illustration of
natural law, which has been brought forward by Mr Babbage in his
_Ninth Bridgewater Treatise_. The reader is requested to suppose
himself seated before the calculating machine and observing it