Combine crumbs, ½ c. coconut and butter. Blend in 2 egg yolks. Pat mixture into bottom of 2-qt. rectangular baking dish. Bake in moderate oven (350°) 15 minutes. Cool.
Brown remaining coconut in oven.
Dissolve gelatin in boiling water. Add lemon juice. Chill until consistency of thick syrup.
Beat egg whites until frothy. Add sugar gradually, b