quite destroy life, adapts its organs, so far as
tney are adaptable, to the altered circumstances.
If there is food at hand, and enemies are not
present, the animal will have time to develop
any peculiarities favourable to the new conditions
that have hitherto lain dormant; and if the
change has affected a race, the next generation
will be not unlikely to have some individuals
modified in a yet more favourable way. We
may thus ultimately obtain a permanent variety,
which is to all intents and purposes a species.
If you are content to take the exposition of M.
de Maillet as an illustration pointing to the
direction in which a change in the proportions
and organs of animals may extend and become
permanent, it seems to be absurd and
impossible.

The idea of the derivation of one so-called
species from another, the two being unlike in
what are regarded as essential characters, is
necessarily fundamental with all naturalists
who are not inclined to admit that new species
have been abruptly introduced from time to
time upon the earth, to fill up acknowledged
gaps in creation, or to take the place of others
which have either died out from actual exhaustion
and old age, or which are to be driven out
by the new arrival.

What is generally understood by a species, is
a group of animals or plants having certain
peculiarities of structure in common, and from
which other like animals or plants are naturally
derived. When two individuals, a male and
female belonging to two different groups, can be
induced to breed together, the result is
considered a hybrid, and two such hybrids, if male
and female, will rarely breed together and
produce young. The horse and the ass producing
the mule afford an illustration too obvious to
require more than mere mention.

But it must not be forgotten that in many
animals, such as dogs, horses, pigeons, and others
that are domesticated, there is enormous difference
between different breeds or varieties, sometimes
amounting to more than the difference
between some of the groups we call species.
Thus there arises a very important question:
What is the essential difference between a
species and one of those varieties which, having
assumed a certain structure in successive
generations, always transmits such structure? This
kind of variety is called permanent, to distinguish
it from that which is modified in each
successive generation. What, then, is the
difference between a species and a permanent
variety.

If we assume that there is an essential difference,
we must suppose that in each case there
is some unknown but defined limit beyond which
no further change can occur. As difference of
size, shape, and colour; difference of bone,
muscle, and nerve; difference of habit, instinct,
and intelligence; all certainly do occur in the
case of permanent varieties, it is very difficult,
if not impossible, to say what other differences
may not be produced if sufficient time be allowed.
If, on the other hand, there be no limit to variety,
there can be no such thing as essential difference
between species, and one may be derived
from another.

But, supposing this possible, in a few simple
cases can the law be assumed as general? In
other words, if a wolf may originally have been
the parent of the whole race of dogs, must we
conclude, as De Maillet did, that the merman, if
there ever was one, was the original founder of
the human race, and the flying-fish the
commencement of bird life? Such a monstrous
conclusion would require a powerful chain of
argument to induce any of us to believe it.

Here, then, step in the naturalists, who are
unable to believe that species have been
introduced by successive isolated acts of creation,
since this notion involves a want of continuity
and harmony in the great system of nature.
They endeavour to illustrate and explain in what
way the divergence from an original form, the
gradual production of an improved form, or in
some cases the reduction to a lower form of
organisation, has taken place.

De Maillet's idea was indeed vague enough,
but not without a fair amount of ingenuity.
Lamarck, one of the most celebrated naturalists
of modern times, followed out the idea and
ripened it into a system and theory. Another
theory was put forward, a few years ago, in
England, in a very popular book, Vestiges of
the Natural History of Creation; and very lately
one of our most ingenious and most sound
geologists (Mr. Charles Darwin), who is also an
excellent naturalist, has advanced a modification
of it which is worthy of all consideration.

Lamarck's view of the cause of passage of
one species into another was as follows. He
considered that the production of a new organ
in an animal frame is the result of some new
want, and that to satisfy this want a new movement
was introduced, and an attempt made by
the animal to supply the want. Thus an intelligent
and strong-willed slug, originally without
tentacula or feelers, would tend to push forward
the head in advance of the body, until by this
effort some approach was made to the existence
of such organs. Now, since all peculiarities of
structure are transmitted by parents to their
offspring, the young of such snail would have
rudimentary feelers which it, could develop by
similar means into more complete examples.

Such is, in a few words, the Lamarckian
doctrine of the transmutation of species by gradual
derivation and the improvement of individuals.
By an exertion of the will, constantly operating,
portions of nervous and other animal fluids are
supposed to be determined towards particular
parts of the body, and the result is the production
of an organ such as circumstances require.

In the Vestiges, the author supposes that
new species are the occasional offspring of
others long since established—a view not without
attraction when placed in the light
prepared for it by the author, and with all his
illustrations around it, but hardly bearing
interpretation into the every-day language of
ordinary existence.