Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III THE THEORY OF EVOLUTION (Continued) The Evidence From Embryology The Recapitulation Theory At the close of the eighteenth, and more definitely at the beginning of the nineteenth, century a number of naturalists called attention to the remarkable resemblance between the embryos of higher animals and the adult forms of lower animals. This idea was destined to play an important role as one of the most convincing proofs of the theory of evolution, and it is interesting to examine, in the first place, the evidence that suggested to these earlier writers the theory that the embryos of the higher forms pass through the adult stages of the loweraniinals. The first definite reference1 to the recapitulation view that I have been able to find is that of Kielmeyer in 1793, which was inspired, he says, by the resemblance of the tadpole of the frog to an adult fish.2 Thjs suggested that the embryo of higher forms corresponds to the adult stages of lower ones. He adds that man and birds are in their first stages plantlike. Oken in 1805 gave the following fantastic account of this relation: Each animal ‘metamorphoses itself through all animal forms. The frog appears first under the form of a mollusk in order to pass from this stage to a higher one.The tadpole stage is a true snail; it has gills which hang free at the sides of the body as is the case in Unio pictorum. It has even a byssus, as in Mytilus, in order to cling to the grass. The tail is nothing else than the foot of the snail. The metamorphosis of an insect is a repetition of the whole class, scolopendra, oniscus, julus, spider, crab. 1 The earlier references of a few embryologists are too vague to have any bearing on the subject. - Autenrieth in 1797 makes the briefest possible reference to some su…