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§ 1. Meaning of the Word, or the Idea of Species.
It is obviously essential to any intelligent answer to the question whether all the varieties of. men are of one species, that we should be able to tell what a species is. This is a point of very great difficulty. Naturalists not only differ in their definitions of the term, but they differ greatly in classification. Some assume a spot on the wing of a butterfly, or a slight diversity of plumage in a bird, as proof of difference of species. Some therefore divide into six or eight species what others comprehend in one. Nothing there-fore can be done until men come to a common understanding on this subject, and the true idea of species be determined and authenticated.
General Characteristics of Species.
Before considering the various definitions of the term, it is proper to remark that there are certain characteristics of species which at least, until of late, have been generally recognized and admitted. (1.) Originality, i.e., they owe their existence and character to immediate creation. They are not produced by physical causes, nor are they ever derived from other genera or species. They are original forms. This is admitted by naturalists of all classes. Such is the doctrine of Cuvier, Agassiz, Dr. Morton, and of those who hold that the varieties of the human race are so many distinct species. They mean by this that they had different origins, and are not all derived from a common stock. Every species therefore, by general consent, has had a single origin. (2.) Universality, i.e., all the individuals and varieties belonging to the same species have all its essential characteristics. Wherever you find the teeth of a carnivorous animal, you find a stomach able to digest animal food, and claws adapted to seize and hold prey. Wherever you find fins to effect motion in water, you find a breathing apparatus suited to the same element. The species is transmitted whole and entire. It is the same in all individuals belonging to it, and in that sense universal. (3.) Immutability, or permanence. By this is meant first, that one species is never lost or merged in another; and secondly, that two or more species never combine so as to produce a third. The rose cannot be merged into the tulip; nor can the rose and tulip be made to produce a new species, which is neither the one nor the other. The only permanent transmissible forms of organic life, are such as constitute distinct species. Immutability, therefore, or the power to perpetuate itself, is one of the indispensable characteristics of species. This, 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 were 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 organic life. (5.) Notwithstanding the ingenious and long continued 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 espèces ne s’altèrent point, ne changent point, ne passent point de l’une à l’autre; les espèces sont Fixes.”101101De la Longevitè Humaine, etc., par P. Flourens, Paris, 1855. 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 species which has not existed as distinct from the beginning, and which is not immutable in its essential characteristics, and which is not 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 characteristics 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 forms 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.” Agassiz102102Principles of zoölogy, p. XIV. 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 included all those animals which are supposed to have arisen in the first instance from a single pair. And to the same effect Dr. Carpenter 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 peculiarity 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 community 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 question is, are Mongolians, Africans, and Caucasians all derived from a common parent? And in the second place, although community of origin would prove identity of species, diversity of origin would not prove diversity of species. All the varieties of the horse and dog would constitute one species for each class, although they had been created as they now are. Species means kind, and If two animals are of the same kind they are of the same species, no matter what their origin may have been. Had God created one pair of lions in Asia, another in North Africa, another in Senegal, they would all belong to one species. Their identity of kind would be precisely the same as though all were descended from one pair. Dr. Morton's definition of species as “a primordial organic form,” has obtained general acceptance. It is, however, liable to objection on the ground of the ambiguity of the word form. If by “form” be understood external structure, the definition is unsatisfactory; if we understand the word in its scholastic sense of essential and formative principle, it amounts to the same thing which is more distinctly expressed in other terms. Agassiz gives another and much more satisfactory idea of the nature of species, when he refers to an immaterial principle as its essential element, and that to which the sameness of the individuals and varieties embraced within it is to be referred.103103Principles of zoölogy, p. 9. He says: “Besides the distinctions to be derived from the varied structure of organs, there are others less subject to rigid analysis, but no less decisive, to be drawn from the immaterial principle, with which every animal is endowed. It is this which determines the constancy of species from generation to generation, and which is the source of all the varied exhibitions of instinct and intelligence which we see displayed, from the simple impulse to receive the food which is brought within their reach, as observed in the polyps, through the higher manifestations, in the cunning fox, the sagacious elephant, the faithful dog, and the exalted intellect of man, which is capable of indefinite expansion.” Again, he says:104104Ibid. p 43. “The constancy of species is a phenomenon dependent on the immaterial nature.” “All animals,” he says, “may be traced back in the embryo to a mere point upon the yolk of an egg, bearing no resemblance whatever to the future animal. But even here an immaterial principle which no external influence can prevent or modify, is present, and determines its future form; so that the egg of a hen can produce only a chicken, and the egg of a codfish only a cod.” Professor Dana says:105105Bibliotheca Sacra, 1857. p. 863. “The units of the inorganic world are the weighed elements and their definite compounds or their molecules. The units of the organic are species, which exhibit themselves in their simplest condition in the germ-cell state. The kingdoms of life in all their magnificent proportions are made from these units.” Again,106106Bibliotheca Sacra, 1857, p. 861. “When individuals multiply from generation to generation, it is but a repetition of the primordial type-idea; and the true notion of the species is not in the resulting group, but in the idea or potential element which is at the basis of every individual of the group.” Here we reach solid ground. Unity of species does not consist in unity or sameness of organic structure, in sameness as to size, colour, or anything merely external; but in the sameness of the immaterial principle, or “potential idea,” which constitutes and determines the sameness of nature. In the initial point on the yolk of the egg, there is no difference of form, no difference discernible by the microscope, or discoverable by chemical analysis, between one germ and another; between the initial cell of the bird and that of the fish. And yet the whole difference is there. The difference, therefore, cannot exist in what is external (although within certain limits and in further development it is manifested externally), but in what is immaterial. So that where the immaterial principle of Agassiz, or the potential idea of Dana, is the same, the species is the same; where the immaterial principle is different, the species is different.
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