retrogressed by the way, and that those that reached the farthest limits, did not remain altogether unchanged, but changed somewhat as ages passed and generations lived and died; those that remained in the original habitat having changed least, those that wandered farther having changed more, and those that wandered farthest having changed most, and this for the reason that though the environment nowhere remained absolutely unaltered, yet for those that travelled farthest it altered most; so those Aryans who dwell in or near the original habitat of the race have changed least, those who halted by the way have changed more, and those that journeyed farthest to the West, or diverged to the North or South, have changed most. So also in the march of life, the lowest organisms may be considered as having stayed behind at or near the original starting-point; the sponges as having diverged from the main road at an early period; the Cœlenterates, the Mollusks, the Annulosa to have halted by the way at a later stage; whereas the Vertebrates, with mammals at their head, and man at the head of the mammals, may be considered as having reached the farthest limits. But just as it becomes increasingly difficult the farther we penetrate into historical antiquity to trace the descent of the nations of any race of human beings,—the Teutonic for example,—not only for the reason that the peoples who have travelled farthest have changed so much, have undergone evolution, and because the peoples who halted by the way or stayed behind have changed also, but because some of the links of the chain are broken, because some of the nations which halted by the way are lost and cannot be recognized, or because they have perished utterly in the struggle for existence; so also the farther we penetrate into geological antiquity, the harder it becomes to trace the descent of species, the more numerous become the
