The Los Angeles District Attorney's office--faced with conflicting evidence and testimony as well as the expiration of the statute of limitations governing animal abuse--has dropped its civil investigation of alleged chimpanzee abuse on the set of "Project X," John Lynch, head of the D.A.'s environmental crimes division, said Thursday. "In no way was there overwhelming evidence that there was abuse," said Lynch. He said that civil charges weren't filed because there was strong evidence and testimony both supporting and disputing the allegations. The D.A.'s office originally sought to file criminal charges against six animal trainers who worked on the 20th Century Fox film, but found that the 1-year statute of limitations governing misdemeanor animal abuse had expired. Said Lynch: "It was a tough call. But the good thing is that it made the movie industry examine the way animals are treated on movie sets. In our minds, we have accomplished most of what we could have done had we filed charges." . . . In a related matter, Jack Valenti, president of the Motion Picture Assn. of America, has asked Robert Rush, general manager of the City of Los Angeles Department of Animal Regulation, to suggest guidelines that the film and television industry might adopt to help avoid animal cruelty during production. Rush, who brought the "Project X" matter to the attention of the district attorney last year, criticized the role of the American Humane Assn. in the overseeing animal treatment on the movie. He is trying to replace the humane association as the entertainment industry's animal welfare watchdog with the International Society for Animal Rights, which Rush said Thursday will help draft the new industry guidelines.