The first is based on the frequent occurrence of "rudimentary," "fragmentary," or "vestigial" structures in animals and plants, which, although now seemingly useless, or even harmful, to their possessors, may be assumed to have been of service to their ancestors, but under changed conditions to have been thrown out of work by Natural Selection, and atrophied by disuse. Such are--the splint-bones of the horse, representing lost digits,--the rudimentary legs of some whales and serpents,--the _mammae_ and mammary glands of male mammals; and in the vegetable kingdom,--the aborted pistil in male florets of some _compositae_,--the useless corolla of certain wind-fertilized flowers, as _plantago_, and indeed the whole floral apparatus of plants which, like Wordsworth's pet the Lesser Celandine,[187] seldom ripen their seeds, but depend on other methods of propagation. The other fact cited on behalf of Darwinism is unquestionably very striking. In the course of their embryonic development, and even in the initial stages of their life after birth, higher animals pass through various phases in which they exhibit the characteristics of lower forms. Thus all life starts from a cell, in which there is nothing to shew whether it is ever to be anything more than a cell, or is to evolve a plant or animal,--nor, in this latter case, what sort of animal it is to be--a mollusc, for instance, a frog, or a mammal. At a later stage[188] it is impossible to distinguish the embryos of lizards, birds, and mammals except by size. Even the human fetus at an early period bears vestiges of gill-clefts or arches, pointing to an aquatic existence. When the extremities come to be developed,[189] "The feet of lizards and mammals, the wings and feet of birds, no less than the hands and feet of man, all arise from the same fundamental form." The young of flat-fish such as soles and turbots, when they leave the egg are not flat, but shaped like ordinary fish, and they wear their eyes in the normal fashion, one on each side of their head, not both on the same side like their parents--whose form however they presently by degrees assume. Young lions and black birds are spotted, showing their affinity respectively to panthers and thrushes--and so on in numberless instances. All such features, it is assumed, indicate the _phylogeny_ of each animal, or the history of the race to which it belongs. As Professor Milnes Marshall succinctly put the matter:[190] The phases through which an animal passes in its progress from the egg to the adult are no accidental freaks, no mere matters of developmental convenience, but represent more or less closely ... the successive ancestral stages through which the present condition has been acquired. Evolution tells us that each animal has had a pedigree in the past. Embryology reveals to us this ancestry, because every animal in its own development repeats this history, climbs up its own genealogical tree.