The question, Why are not new species continually produced? may be aptly met by another. How, consistently with the theory, is it possible they should? Natural Selection is represented as acting 'solely by accumulating slight successive favourable variations,' as taking only short and slow steps. By what possibility, then, can it suddenly produce modifications sufficiently conspicuous to mark off a new species? New species may be, and indeed are, constantly in process of formation on all sides, under our very eyes, without our being aware; for since the process requires ages for its accomplishment, it must needs be imperceptible by the keenest observation. So that even when a new species is completed, it is not recognised as new, so minute is the difference between the perfection to which it has attained, and the imperfect state in which we and our fathers before us had long known it. 'Why, however, since, according to the theory of Natural Selection, an interminable number of intermediate forms must have existed, linking together all the species in each group by gradations as fine as are our present varieties--why do we not see these linking forms all around us?' To this objection the very theory against which it is urged affords a partial and almost adequate reply, the deficiencies of which are besides to some extent supplied by embryology and geology, and to a farther extent accounted for by the meagreness of the geological record. Natural selection for survival necessarily implies extinction of all that are not selected to survive, so that fossil remains are now the only procurable evidence that any of these latter that have long been extinct ever existed. But very many organic beings are incapable of being preserved in a fossil condition, while of those which can be so preserved 'the number of specimens in all our museums is absolutely as nothing compared with the countless generations of countless species that must have existed.' It should be recollected, too, that among still existing forms are to be included several which result from uterine transformation, and are never found alive except _in utero_.