Sunday, August 10, 197.5 By DONALD C. DRAKE li"`lLir~~i' MpulCrll IV)'?ter SAN JOSE de OCOA, Dominican Republic - "MariLIN!' MariLIN!" the grandmother yelled to the g-year- old girl with the sad, beautiful face. "We have visitors. They have come to see the twins. Go quickly. Prepare them at once." The girl disappeared, and soon the room was filled with people running in and out of doorways with wet washcloths and baby clothes. Neigh- bors crowded outside the house and peered tnrough the open windows and doorways. They wanted to know who these foreigners were who had come down tneir street in a new car with Sister Cecilia. It was 1 p.m., midway through the nnd Clara Rotiri::uez - were separated in un operation that-made medical history Se[?t. 18, 197-1, at Phiiudelphia's Childrc.