SPECIES AND RACE IN THE NATURAL SCIENCES.
I. The question of the unity or multiplicity of the human species
may be stated in the following terms: are the differences which
distinguish the human groups characteristic of _species_ or of _race_?
It is evident that the question depends entirely upon the two words
species and race. It is then absolutely necessary to determine
as accurately as possible the sense of each, and yet there are
anthropologists, such as Knox, for instance, who declare that any
discussion or investigation in connection with this subject is idle.
There are others, like Dr. Nott, who would suppress the race and
only establish various _categories of species_. In order to support
their doctrines these authors ignore the work which has been carried
on for nearly two centuries by the most illustrious naturalists, and
the innumerable observations and experiments made by a vast number of
eminent men upon plants and animals.
In fact the theory of species and race has not been formed _à
priori_, as it has been too often falsely asserted, but has been
gradually acquired, and in a strictly scientific manner.
II. The word _Species_ is one which exists in all languages which
possess abstract terms. It represents, therefore, a general common
idea. The idea is, in the first place, that of a great outward
_resemblance_; but even in ordinary language that is not all. The
idea of _filiation_ is connected, even in the most uncultivated
minds, with that of resemblance. No peasant would hesitate to regard
the children of the same parents as _belonging to the same species_
whatever real or apparent differences might distinguish them.
Science has in reality done nothing more than define the idea of
which the public had merely a vague consciousness, and it was
not till very lately, and after a very curious oscillation, that
she succeeded in doing so. In 1686, Jean Ray, in his _Historia
Plantarum_, considered that those plants which had a common origin
and could be reproduced by seed belonged to the same species,
whatever their apparent differences might be. He only took filiation
into account. Tournefort, on the contrary, who in 1700 was the first
to make a clear statement of the question, termed the collection
of plants a _species_ which were distinguished by some particular
character. He relied only on resemblance.
Ray and Tournefort have had from time to time a few imitators,
who, in their definition of species, have clung to one of the two
ideas. But the immense majority of zoologists have been aware of the
impossibility of separating them. To convince ourselves of this fact
it is only necessary to read the definitions which they have given.
Each one of them, from Buffon and Cuvier to MM. Chevreul and C. Vogt
has, so to speak, proposed his own. Now, however they may differ in
other respects, they all agree in this. The terms of the definitions
vary, each endeavours to represent in the best manner possible the
complex idea of species; some extend it still further, and connect
with it the ideas of cycle and variation: but in all the fundamental
idea is the same.
In a case of such difficulty as that of finding a good definition
for a combination of ideas, the latest comer always hopes to improve
upon his predecessors. For this reason I have also given my formula:
“Species is a collection of individuals more or less resembling
each other, which may be regarded as having descended from a single
primitive pair by an uninterrupted and natural succession of
families.”
In this definition, as also in that of some of my colleagues, among
others of M. Chevreul, the idea of resemblance is made of less
importance and subordinate to that of filiation. The fact is that
there never is an identity of characters between one individual and
another. Putting aside the variations resulting from age and sex, it
is at once evident that all representatives of the same specific type
differ in some points. Although these differences are very slight,
they constitute _individual traits_, _shades_ as Isidore Geoffroy
said, which enable us to distinguish between two of the same species.
But the differences are not confined within these limits. The
specific types are _variable_, that is to say, every kind of physical
character is modified in their derivatives and, under the influence
of certain conditions, to such an extent as to make it often very
difficult to recognise their unity of origin. This, again, is a fact
upon which all naturalists agree. Blainville even, who, defined
species as “the individual repeated and continued through time and
space,” distinctly recognised this _variability_; for the individual
is perpetually undergoing modification, and does not retain its
similarity during the various stages of life. He admitted, moreover,
the existence of distinct races.
The _variability of species_ has also been the subject of animated
discussion among naturalists. The memorable contention which arose
upon this subject between Cuvier and Geoffroy is not yet forgotten,
a struggle considered by Goethe as more important than the gravest
political events. In the present day a school to which many of the
most illustrious names in England, Germany and elsewhere belong,
has taken up, with certain modifications, the ideas of Lamarck
and Geoffroy; it gives support to them from retaining the term
_variability of species_.
There is a grave confusion of words in this formula. Lamarck,
Geoffroy, Darwin and his school, consider the species not only as
_variable_ but as _transmutable_. The specific types are not merely
_modified_, they are _replaced_ by new types. _Variation_ is in
their estimation only a phase of the very different phenomena of
_transmutation_.
I shall discuss these theories presently. I shall now confine
myself to the remark that _true variability_, admitted even by the
defenders of _dogmatic invariability_, by Blainville, for example,
a variability which I fully accept, has nothing in common with the
_transmutability_ of Lamarck, Geoffroy and Darwin. Let us briefly
determine the limits of this variability.
III. When an individual trait is exaggerated and passes a limit
always very loosely defined, it constitutes an exceptional character
which clearly distinguishes the individual affected by it from all
those most nearly resembling it. This individual constitutes a
_Variety_.
The same term must be applied to all those individuals, which, like
certain plants reproduced by slips, grafts, or shoots, derive their
origin from the first exceptional individual, without having the
power of transmitting their distinctive characters by means of normal
generation. I borrow from M. Chevreul a curious example of these
_multiple varieties_. In 1803 or 1805, M. Descemet discovered in his
garden at Saint Denis, in the midst of a bed of acacias (_Robinia
pseudo-acacia_) an individual without thorns which he describes
under the epithet _spectabilis_. It is to the multiplication of
this individual by the art of the gardener that all the _thornless
acacias_, now distributed over every part of the globe, owe their
origin. Now these individuals produce seeds, but if the seeds are
sown they only yield _thorny acacias_. The _acacia spectabilis_ has
remained a _Variety_.
The latter may then be defined as:—“An individual or a number of
individuals belonging to the same sexual generation, which is
distinguished from the other representatives of the same species by
one or several exceptional characters.”
It will readily be seen how great the number of varieties in one
species may be. There is, in fact, scarcely any either external or
internal part of an animal or plant, which cannot be exaggerated,
diminished or modified in a thousand ways, and each of these
exaggerations, diminutions or modifications will characterise a fresh
variety, with the one condition of its being sufficiently marked.
IV. When the characters peculiar to a variety become _hereditary_,
that is to say, when they are transmitted from generations to the
descendants of the first modified individual, a _race_ is formed.
For example, if a _thornless acacia_ ever reproduced by seed, trees
resembling itself and enjoying the same power, then the Acacia
spectabilis would cease to be a simple variety, and would have become
a race.
The race, then, will consist of:—“A number of individuals resembling
each other, belonging to one species, having received and
transmitting, by means of sexual generation, the characters of a
primitive variety.”
Thus the _Species_ is the point of departure; the _variety_ appears
amongst the _individuals_ of which it is composed, and, when the
characters of this variety become hereditary, a _race_ is formed.
Such are the relations which, according to all naturalists, “from
Cuvier to Lamarck himself,” as Isidore Geoffroy said, exist between
these three terms. We have here a fundamental idea which we should
never lose sight of in the study of the questions with which we are
engaged. From neglect of it men of the highest distinction have
failed to understand most significant facts.
We see that the idea of _resemblance_, which is much curtailed in the
_species_, reassumes in the _race_ an importance equal to that of
_filiation_.
We see also that the number of races which spring directly from one
species may be equal to the number of varieties of the same species,
and consequently very considerable. But this number has a tendency
to increase still further to an indefinite extent. In fact, each
of these _primary races_ is susceptible of fresh modifications,
which may either extend no further than one individual, or become
transmissible by means of generation. Thus _secondary_ and _tertiary
varieties_ or _races_ come into existence. Our plants and domestic
animals furnish innumerable examples of these facts.
V. By reason of races originating in this manner from one another,
and from their multiplication, they may assume differential
characters which become more and more decided. But however numerous
they may be, and whatever differences there may be between them, and
however far they may seem to be removed from the primitive type, they
nevertheless, still form part of the species from which the primitive
races derived their origin.
On the other hand, every species comprises, independently of the
individuals which have preserved their primitive characters, all
those which compose the primary, secondary and tertiary, etc., races,
derived from the fundamental type.
In other words the _species_ is the _unit_ and the _races_ are the
_fractions_ of this unit. Or again, the _species_ is the _trunk of
the tree_, of which the _several series of races_ represent the
_principal_ and _lesser branches_ and the _twigs_. The general unity
and relative independence of the trunk and the branches of the tree
represent in an obvious manner the connections existing between the
species and its races.