The British Academy of Sciences, after an 18-month study, has recommended to parliament that British rock stars be prohibited by law from selling their semen to commercial sperm banks. The Academy states that restrictions are necessary because it fears that lack of controls could lead to a "sperm bank pop star war." What the scientists are worried about is that rock idols such as Mick Jagger, David Bowie or Paul McCartney might sell their sperm to the frozen banks which would, in turn, advertise it - selling it to ands of female groupies wishing to become pregnant. The Academy says it does not oppose the idea of thousands of Mick Jagger offspring being fathered. What is worrisome, says the Academy, is that when these children grow up, they could marry one another without knowing that they have the same father. This, the Academy warns, is incest - and could lead to genetic problems in the future. The Academy's report has been turned over to the House of Commons for er probing.