Preheat oven to 450°. Stir together cornmeal and sugar in a large bowl; make a well in center of mixture. Whisk together eggs, sour cream, and butter; add to cornmeal, stirring just until dry ingredients are moistened. Fold in blackberries. Spoon batter into 2 lightly greased 12-cup muffin pans, filling three-fourths full.
Bake at 450° for 15 to 17 minutes or until tops are golden brown. Cool in pan on a wire rack 5 minutes.