McInally, who made his first international appearances in Scotland's back-to-back warm-up wins over Italy last month, is suffering from a neck complaint that "necessitates a prolonged period of recovery beyond the competition", a statement said.
Glasgow Warriors hooker Bryce -- a back-row convert who made his Scotland debut as a loose forward on last year's summer tour -- has been brought in with the Scots gearing up to face Japan in their opener in Gloucester on Sept. 23.
South Africa, Samoa and the United States are also in Pool B.
(Writing by Justin Palmer; editing by Martyn Herman)
