FIGURE 3.5 Prenatal development (a) The embryo grows and develops rapidly. At 40 days, the spine is visible and the arms and legs are beginning to grow. (b) By the start of the ninth week, when the fetal period begins, facial features, hands, and feet have formed. (c) As the fetus enters the sixteenth week, its 3 ounces could fit in the palm of your hand.
All photos: Lennart Nilsson/Albert Bonniers Publishing Company