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T is the great unquestioned addition to Darwinism made by Haeckel that the history of the embryo is shown to recapitulate the history of its ancestral species. As stated by Haeckel's authorized expositor, Mr. Lester Ward, the law has a fascinating simplicity. The development of successive species being the mechanical cause of the development of the embryo, every transmutation undergone by the former in the course of ages is passed through by the latter. From the primary cell onward, the successive species are faithfully reproduced by successive stages in the growth of the embryo. Man is thus first of all an amœba, he advances to the humble condition of a worm, is transformed into a lamprey, grows into a kind of fish, is fortunately only a bit of a reptile, is promoted to be a marsupial, a lemur, an ape, a man-ape, before he emerges in distinctly human form. So far, Haeckel. Other naturalists find the parallel more complex. In no case, according to Prof. Henry Drummond, is the recapitulation of the past complete. "Ancestral stages are constantly omitted, over-accentuated, condensed, distorted, or confused; while new and undecipherable characters occasionally appear." Haeckel has no difficulty in accounting for these new and undecipherable characters. They are the priceless records of formerly existing but now extinct species. By their aid we can recover the vanished past. It was a wonderful feat when Kant predicted, from certain disturbances in the planetary orbits, that the planet Neptune would one day be discovered. It was a great thing when Owen was (rightly or wrongly) believed to have reconstructed the moa from a thigh bone, or when from a few small molar teeth found in Germany and North America two lost species were built up. Haeckel has shown a still more daring exercise of the scientific imagination in confidently assuming the existence of species of which no trace has ever been found. Of the twenty-one species between the moner and man nearly one half are hypothetical. Not even their fossil remains have been discovered. But the German idealist betrays no doubt of their reality. That they are vouched for by answering stages in the growth of the embryo is evidence enough. In at least one case later research seems to have vindicated his prevision.

The analogy is strictly limited to species in the line of descent. No creature is the inheritor of the whole pre-existent organic creation. Man himself, the crown of Nature and its lord, is heir to only three of the seven animal subkingdoms. Never having been a