A 64% rise in earnings per share for the second quarter of 1987 was posted by Los Angeles-based Caesars World. Revenue also was higher. For the first six months, profit took a big jump, compared to the same period a year ago. It was the 15th consecutive quarter in which net income increased over the comparable quarter of the preceding year, a spokesman said. Caesars Palace, Las Vegas, was the principal contributor to the earnings increases, he added.