DEVELOPMENT OF THE ORGANISM
narrow neck, which has nothing to do with the neck of the young child. Along the sides of the neck there are two series of gill slits, and, just as in the tadpole, these become covered by flaps of skin that grow back from the head and join the trunk. The neck indentation is thus obliterated, and the head passes without a break into the trunk, just as it does in the older tadpole. The blood vessels at the sides of the gill clefts resemble exactly those of the tadpole. There are four of them on each side, and, with accurate imitation of the tadpole, the third on each side drops out. The salamander retains the four throughout life, but its near cousin, the newt, drops out the third, as does the frog. Thus the story of man’s development from a water animal and his gradual closing up of his gill clefts is accurately repeated in the womb, and the distortion of this story by the development of the placenta is easily recognised. We find the same history if we study the development of the young lizard within its mother; but here no placenta is developed, and the egg is afterward laid, but development has begun long before that. So by comparing the life histories of different animals belonging to the same phylum we can separate the secondary accretions from the original story and thus recover the true ancestral history.
To return to human development: As this proceeds the limbs grow out and the embryo comes to resemble an ordinary four-footed animal, but the fingers and toes are at first webbed like those of a frog. At this stage there is a well-developed tail, and later there is a complete covering of hair, resembling the hairy skin of an ape. At birth the big toe is widely separated from the other toes, just as is the big toe of an ape, and the legs curve inward at the ankles, so that when the child is held upright only the outer edge of the sole rests on the ground. This arrangement of the
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