weeks 9-38. At beginning, weighs less than an ounce. 4 months, fetus is 4 – 8 ounces (can feel it move!). Tube forms, one end becomes the brain, the rest the spinal cord. Distinct brain structures begin to grow, begins to regulate body functions. In third month, hormone in testes secreted that causes some cells to become penis and scrotum. If absent, vagina and labia forms. Heart rate variability at about 6 months. Moves about once a minute. Can hear mom’s heartbeat and voice. Can taste flavors in amniotic fluid. Enough light passes through abdominal wall for fetus to see. Develop memory.