"[T]he appellee and certain “amici curiae” argue that the fetus is a person within the language and meaning of the Fourteenth Amendment. In support of this, they outline at length and in detail the well-known facts of fetal development. If this suggestion of personhood is established, the appellant’s case of course, collapses for the fetus’ right to life is then guaranteed specifically by the Amendment. The appellant conceded as much on reargument”"