What does this quote mean ?

Hi. What the speaker is saying is that he is not worthy of living any more. "tainted wether of the flock" means the weakest animal in the group. Meetest for death means the best one to die. The weakest kind of fruit etc. means that the rotten fruit falls and leaves the best to ripen. He ends by telling Banio that he should live and write the speaker's epitaph - the saying to go on his grave.