Note D — Chapter VI · IRREGULAR OPENINGS.
Reading edition
If 10.., P. takes P., then 11. R. takes P., and Black could not challenge the Queen with 11.., Q. to Q. B's 4th, because of 12. R. to Q. B's 4th. Nor could 10.., K. to K's 2d be played, because of 11. P. takes P., and 11.., Q. takes B. P. would be answered with 12. R. takes Kt. winning the Queen, and as the continuation in the text is hopeless, there remains the only alternative of 10.., Castles, with a good enough game, all things considered.