question is, are Mongolians, Africans, and Caucasians all derived fi'om a common parent ? And in the second place, although com- munity 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, altliough 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 or- ganic form," has obtained general acceptance. It is, however, liable to objection on the ground of the ambiguity of the word/on??. 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.^ He says : " Besides the dis- tinctions 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 dis- played, 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 capa- ble of indefinite expansion." Again, he says:^ " 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 what- ever to the future animal. But even here an immaterial principle ivhich 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 : ^ " The units of the inorganic world are the weighed
I Principles of Zoology, p. 9. 2 ]bid. p. 43. « Bibliotheca Sacra, 1857, f • 863.
roL. II. 6
8~ PART II. Ch. IV. — unity OF THE HUMAN RACE.
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,^ " When individuals multiply from generation to genera- tion, it is but a repetition of the primordial type-idea ; and tlie 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 o-roup." 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 discerni- ble by the microscope, or discoverable by chemical analysis, between one crerm and another ; between the initial cell of the bird and that of the fish. And yet the whole difference is there. The differ- ence, therefore, cannot exist in what is external (although within certain limits and in further development it is manifested exter- nally), 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.
§ 2. Evidence of Identity of Species. Such being the case, the only question is, how can we deter- mine whether the immaterial principle which constitutes and deter- mines the species, be the same or different. Aside from divine revelation, this can be ascertained : (1.) Partly from the organic structure. (2.) Partly from the ^vo-ts, or physical nature. (3.) Partly from the ^vxn, or psychological nature. (4.) Partly from permanence and capability of indefinite propagation.
Organic Structure.
The first evidence of the identity of species is to be sought in the o-SjLia, or the organic structure. The evidence of design is impressed upon all the organized bodies in the universe, and especially upon the bodies of all animals. Those intended to live on the dry ground, those intended to live in water, and those intended to fly in the air, have their animal frame adapted to these several modes or conditions of existence. There is also clear evidence of
1 Bibliotheca Sacra, 1857, p. 861.