2. _Corroborative:_ a) The Argument from Morphology (Structure). The resemblance of the structure of various animal types is asserted to imply a community of descent. "Large groups of species, whose habits are widely different, present certain fundamental likenesses of structure. The arms of men and apes, the fore-legs of quadrupeds, the paddles of whales, the wings of birds, the breast-fins of fishes, are constructed on the same pattern, but altered to suit their several functions. Nearly all mammals, from the long-necked giraffe to the short-necked elephant, have seven neck-bones; the eyes of the lamprey are moved by six muscles which correspond exactly to the six which work the human eye; all insects and Crustacea--moth and lobster, bettle [tr. note: sic] and cray-fish---are alike composed of twenty segments; the sepals, petals, stamens, and pistils of a flower are all modified leaves arranged in a spire." (Clodd, _"The Story of Creation,"_ p. 102.) These _resemblances_ are looked upon as evidence of a common origin. b) The Argument from Embryology. The individual animal in embryonic development passes through temporary stages which are similar to permanent conditions in some of the lower forms in the same group. Evolutionists believe that these forms were actually possessed by the ancestors of these animals in the course of their evolution. They hold that the changes which take place in the embryos epitomize the series of changes through which the ancestral forms passed. Because the embryos of some four-footed animals have gill-slits, this is pointed out as evidence that land animals are evolved from fishes. c) Geographical Distribution. In geological time, natural barriers have sprung up which separated the species which have since developed. In this way the existence of marsupials (pouched animals--kangaroo, oppossum) [tr. note: sic] on certain limited areas, the limitation of certain plants to certain islands, etc., are explained.