power to perpetuate itself, is one of the indispensable character- istics of species. Tliis, until recently, has been the universally admitted doctrine of naturalists. And notwithstanding the efforts of the advocates of the different theories of development, it still remains the general faith of the scientific world. The leading arguments in support of this doctrine have already been adverted to, when speaking of the theory of Mr. Darwin on the origin of species. Those arguments are briefly the following. (1.) The historical fact that all known species of plants and animals are now precisely what they wei'e as far back as history reaches. The Bible and the records on the Egyptian monuments carry us back to a point thousands of years before the birth of Christ. During this whole period of five or six thousand years species have remained the same. (2.) If we are to receive the facts of geology as authenticated, it is clear that the same permanence has existed from the very beginning of life on our globe. As long as any species exists at all, it exists unchanged in all that is essential to it. (3.) There is an entire and acknowledged absence of all evidence of transmutation ; none of the transition points or links of connection between one species and another is anywhere discoverable. (4.) If species were not thus immutable the animal and vegetable world instead of presenting the beautiful order everywhere visible, would exhibit a perfect chaos of all or- ganic life. (5.) Notwithstanding the ingenious and long contin- ued efforts to render hybrids prolific, such attempts have uniformly failed. The two greatest living authorities on this subject are Dr. Bachman of Charleston, South Carolina, and M. Flourens of the Jardin des Plantes in Paris. " Either hybrids," says the latter, " born of the union of two distinct species, unite and soon become sterile, or they unite with one of the parent stocks and soon return to this type — they in no case give what may be called a new species, that is to say, an intermediate durable species." " Les esp^ces ne s'alt^rent point, ne changent point, ne passent point de I'une a I'autre ; les especes sont Fixes." ^ There is no natural law better authenticated or more generally admitted than that species are immutable and capable of indefinite propagation.
Definitions of Species, No group of animals therefore can be regarded as a distinct spe- cies which has not existed as distinct from the beginning, and which is not immutable in its essential characteristics, and whia^i is not 1 De la Langeviie Humaine^ etc., par P. Flourens, Paris, 1855.
80 PART II. Ch. IV. — unity OF THE HUMAN RACE.
capable of propagating itself indefinitely. These are important landmarks, but they are not sufficient to guide us in all cases to a satisfactory conclusion as to whether given individuals or varieties are of the same or of different species. (1.) Because the origin of these varieties cannot be historically traced. The Caucasian and the negro have existed with their present distinguishing character- istics for several thousands of years. But this does not prove that they differed from the beginning. (2.) Because certain varieties of the same species when once established become permanent, and are capable of indefinite continuance. Several varieties of dogs depicted on the Egyptian monuments centuries before Christ, are precisely what now exist. Naturalists therefore have sought for some precise definition of species, although these attempts have not been generally successful. Cuvier says : " We are under the necessity of admitting the existence of certain foi-ms which have perpetuated themselves from the beginning of the world, without exceeding the limits first prescribed ; all the individuals belonging to one of these forms constitute what is termed a species." De Candolle says : " We write under the designation of species all those individuals who mutually bear such close resemblance to each other as admits of our supposing they have arisen from a single pair." Agassiz ^ says : " Species is founded upon less important distinctions, such as color, size, proportions, sculpture, etc." The objections to these definitions are, (1.) That they do not enable us to distinguish between species and varieties. (2.) They refer almost exclusively to what is external or material, colour, size, proportion, etc., as the criteria, to the neglect of the higher constituents of the animal. Dr. Prichard says, that under the term species are in- cluded all those animals which are supposed to have arisen in the first instance from a single pair. And to the same effect Dr. Car- penter says : " When it can be shown that two races have had a separate origin, they are regarded as of different species ; and, in the absence of proof, this is inferred when we find some peculiar- ity of organization characteristic of each, so constantly transmitted from parent to offspring, that the one cannot be supposed to have lost, or the other to have acquired it, through any known operation of physical causes." The objection to this view of the matter is that it makes community of origin, either proved or inferred, the criterion of sameness of species. But, in the first place, this com- munity of origin cannot in a multitude of cases be established ; and in the case of man, it is the very thing to be proved. The great
1 Principles of Zoology, p. xiv.