the
earth is necessarily most imperfect and fragmentary,--as much so as our
knowledge of the present organic world would be, were we forced to make
our collections and observations only in spots equally limited in area
and in number with those actually laid open for the collection of
fossils. Now, the hypothesis of Professor Forbes is essentially one that
assumes to a great extent the completeness of our knowledge of the whole
series of organic beings which have existed on the earth. This
appears to be a fatal objection to it, independently of all other
considerations. It may be said that the same objections exist against
every theory on such a subject, but this is not necessarily the case.
The hypothesis put forward in this paper depends in no degree upon the
completeness of our knowledge of the former condition of the organic
world, but takes what facts we have as fragments of a vast whole, and
deduces from them something of the nature and proportions of that whole
which we can never know in detail. It is founded upon isolated groups of
facts, recognizes their isolation, and endeavours to deduce from them
the nature of the intervening portions.

_Rudimentary Organs._

Another important series of facts, quite in accordance with, and even
necessary deductions from, the law now developed, are those of
rudimentary organs. That these really do exist, and in most cases have
no special function in the animal oeconomy, is admitted by the first
authorities in comparative anatomy. The minute limbs hidden beneath the
skin in many of the snake-like lizards, the anal hooks of the boa
constrictor, the complete series of jointed finger-bones in the paddle
of the Manatus and whale, are a few of the most familiar instances. In
botany a similar class of facts has been long recognised. Abortive
stamens, rudimentary floral envelopes and undeveloped carpels, are of
the most frequent occurrence. To every thoughtful naturalist the
question must arise, What are these for? What have they to do with the
great laws of creation? Do they not teach us something of the system of
Nature? If each species has been created independently, and without any
necessary relations with pre-existing species, what do these rudiments,
these apparent imperfections mean? There must be a cause for them; they
must be the necessary results of some great natural law. Now, if, as it
has been endeavoured to be shown, the great law which has regulated the
peopling of