(such as the introduction of man), as that one form should be transmuted into another upon fitting occasion, as, for instance, in the succession of species which differ from each other only in some details.  To compare small things with great in a homely illustration:  man alters from time to time his instruments or machines, as new circumstances or conditions may require and his wit suggest.  Minor alterations and improvements he adds to the machine he possesses; he adapts a new rig or a new rudder to an old boat:  this answers to Variation.  “Like begets like,” being the great rule in Nature, if boats could engender, the variations would doubtless be propagated, like those of domestic cattle.  In course of time the old ones would be worn out or wrecked; the best sorts would be chosen for each particular use, and further improved upon; and so the primordial boat be developed into the scow, the skiff, the sloop, and other species of water-craft—­the very diversification, as well as the successive improvements, entailing the disappearance of intermediate forms, less adapted to any one particular purpose; wherefore these go slowly out of use, and become extinct species:  this is Natural Selection.  Now, let a great and important advance be made, like that of steam navigation:  here, though the engine might be added to the old vessel, yet the wiser and therefore the actual way is to make a new vessel on a modified plan:  this may answer to Specific Creation.  Anyhow, the one does not necessarily exclude the other.  Variation and natural selection may play their part, and so may specific creation also.  Why not?

This leads us to ask for the reasons which call for this new theory of transmutation.  The beginning of things must needs lie in obscurity, beyond the bounds of proof, though within those of conjecture or of analogical inference.  Why not hold fast to the customary view, that all species were directly, instead of indirectly, created after their respective kinds, as we now behold them—­and that in a manner which, passing our comprehension, we intuitively refer to the supernatural?  Why this continual striving after “the unattained and dim?” why these anxious endeavors, especially of late years, by naturalists and philosophers of various schools and different tendencies, to penetrate what one of them calls “that mystery of mysteries,” the origin of species?

To this, in general, sufficient answer may be found in the activity of the human intellect, “the delirious yet divine desire to know,” stimulated as it has been by its own success in unveiling the laws and processes of inorganic Nature; in the fact that the principal triumphs of our age in physical science have consisted in tracing connections where none were known before, in reducing heterogeneous phenomena to a common cause or origin, in a manner quite analogous to that of the reduction of supposed independently originated species to a common ultimate origin—­thus, and in various other ways,