Let us now, at long last, praise all those Negro humorists from years gone by. Some still with us, but so many gone. Moms Mabley and Pigmeat Markham and Redd Foxx and Flip Wilson and Bert Williams and Amos 'n' Andy, gone. Stepin Fetchit, gone. Dick Gregory and Richard Pryor and Chris Rock and Steve Harvey and Eddie Murphy and Bill Cosby are very much still with us, though Gregory and Pryor are ailing and far removed from the comic stage. Altogether, through the years, they've held on.