"On comparing these definitions, as given by various naturalists, each in his own language, it will be perceived that there is no essential difference in the various views expressed in regard to the characters by which a species is designated. They all regard it as 'the lowest term to which we descend, with the exception of _varieties_, such as are seen in domestic animals.' They are, to examine the external and internal organization of the animal or plant--they are, to compare it with kindred species, and if by this examination they are found to possess _permanent characters differing from those of other species, it proves itself to be a distinct species_. When this fact is satisfactorily ascertained, and the specimen is not found a domestic species, in which varieties always occur, presumptive evidence is afforded of its having had a primordial existence. We infer this from the fact that no species is the production of blind chance, and that within the _knowledge of history_ no true species, but _varieties_ only, whose origin can be _distinctly traced to existing and well-known species_, have made their appearance in the world. This, then, is the only means within the knowledge of man by which any species of plant or animal _can be shown_ to be primordial. The peculiar form and characters designated the species, and its origin was a necessary inference derived from the characters stamped on it by the hand of the Creator." To all the positions thus far taken by Dr. Bachman, we most cheerfully subscribe; they are strictly scientific, and by such criteria alone do we desire to test the unity of the human family; but we must enter a decided demurrer to the assertion which follows, viz: that, "according to the universally received definition of species, all the individuals of the human race are proved to be of one species." When it shall be shown that all the races of men, dogs, horses, cattle, wolves, foxes, &c., are "varieties only, _whose origin can be distinctly traced to existing and well-known species_," we may then yield the point; but we must be permitted to say that Dr. Bachman is the only naturalist, as far as we know, who has assumed to know these original types. Now, if the reader will turn back and review carefully all the definitions of species cited, he will perceive that they are not based upon _anatomical characters_, but simply on the _permanency_ of certain organic forms, and that this permanence of form is determined by its _history_ alone.