At 5-foot-11, Arnt has straight blond hair and blue eyes. He swims, runs, skis on water and snow, and works out. A law student, the 28-year-old describes himself as easygoing, a creative perfectionist with a good wit, an extrovert. He's not advertising for a girlfriend. His sperm is for sale. Arnt is one of 50 men from Denmark whose sperm sits in one of three metal vats in Manhattan - waiting for a couple or a single mother desperate for a baby. In this case, a Viking baby. The company, Scandinavian Cryobank, has been in business in Denmark for almost...