she announced that she would be selling her flat in london and would move to wherever in the world spider and rosie were , to be near her grandchildren ; and , as time went on , she would drop pointed comments about the lack of grandchildren , the quantity and motility of spider 's spermatozoa , the frequency and positions of spider and rosie 's sexual relations , and the relative cheapness and ease of in vitro fertilization , to the point where spider seriously began to think about not going to bed with rosie anymore , just to spite rosie 's mother .