What is thus true in all the rudimentary stages of organic development is strikingly confirmed by the unalterable condition of all living nature. Plants and animals never diverge, beyond small ascertained limits, from the fixed characters of their families, resisting the effects of every kind of influence, whether proceeding from natural causes or human interference. The lapse of three thousand years has left the embalmed carcasses of men and animals, in Egypt, wrapped and swathed in a material woven from the same species of plants which still flourish on the banks of the Nile. The crocodile and the ibis still drink of its waters. Nothing changed in form or appearance, the swarthy Arab repairs to its cooling fountains to quench his thirst. Nature has been tortured in a thousand ways, to cause her to depart from her long beaten paths; but she is obdurate on every point. Man would improve her kinds, and hybrids are produced; but there the variety ends. Crosses are constantly attempted; but “the hitherto and no farther” is soon approached. Our fruit-bearing trees are coaxed with all the appliances of horticultural skill; and yet in all their seminal and floral organs, the texture of their leaves and bark, the structure of their roots and stem, the rudimentary stock remains one and the same. Domestication has, indeed, wrought wonderful changes and improvements in the breed of many creatures. Horses, oxen, sheep, pigs, dogs, and poultry of all sorts, are increased in bulk, tamed, ameliorated in habit and disposition. But the skeletons of all continue essentially as they were in their natural state; and even the individuals the most widely removed from the primitive type, as exemplified in the canine race, never present any real difference of form in the important organs.—When again abandoned to their own guidance, and the restraints imposed by man are removed, the domesticated animals, one and all, return to their former condition, and speedily resume the instincts and appearance of the jungle and the forest. If such are the unvarying laws of physiology now, the presumption is that they have been the same in all past ages. Creatures are brought from the extremities of the earth—the polar, temperate, and tropical denizens, all mixed up and crossed with each other—food, climate, and treatment, all changed—and, through all, the type of every species continues as before—no transmutation of one kind into another under all the violent tutoring agencies to which they have been subjected. For thousands of years such has been the unswerving course of nature. Would it not clearly be a solecism in reasoning to argue differently over the geological epochs, however indefinite in extent, because, in the far-off regions of space, our eyes can note no change in the relative position of the stars? The things will not compare. Time and space are not co-ordinate terms. And an appeal from positive knowledge to supposed, assumed ignorance does not meet the question.