Here, then, we have a comparison between what takes place in the development of the individual animal in the space of a few years, and what may be supposed to take place in the successive generations of different creatures through untold millions of years. We turn then to the proof, direct or indirect, that races of entirely distinct organisms have resulted from antecedent races by gradual transformation. Direct proof sufficient to establish the progressive modifications of antecedent races into other races is not claimed to exist; yet it is claimed that there are numerous facts of the order required by the hypothesis which warrant our acceptance of it. These facts are the alterations of structure which take place in successive generations of the same species, amounting, in the course of several generations of the same race, to additions and suppressions of parts. These changes among the individuals of the same race, comprehended in what is scientifically called "heredity" and "variation," are exhibited by the transmission of ancestral peculiarities of structure, by their occasional suppression in some individuals of the race and their reappearance in others, and by a difference in the relative sizes of parts. These variations, arising in successive short intervals of time, are said to be quite as marked as those which arise in a developing embryo, and, in fact, they are said to be often much more marked. "The structural modifications proved to have taken place since organisms have been observed is not less than the hypothesis demands--bears as great a ratio to this brief period as the total amount of structural change seen in the evolution of a complex organism out of a simple germ bears to the vast period during which living forms have existed on earth."[73] The difficulty that is thus prepared for the hypothesis of the special creation of species may now be stated. There is a professed conception of the ultimate power which is manifested to us through phenomena. That conception implies omnipotence and omniscience, and it therefore implies regularity of method, because uniformity of method is a mark of strength, whereas irregularity of method is a mark of weakness. "A persistent process, adapted to all contingencies, implies greater skill in the achievement of an end than its achievement by the process of meeting the contingencies as they severally arise." And, therefore, those who adopt the notion of the special creation of species do, it is said, in truth impair the professed character of the power to which they assume that the phenomena of the existence of species are to be referred, whereas the hypothesis of the evolution of species out of other species is much more consistent with the professed conception of the ultimate power.