Marseillais chess

Marseillais chess (also called Double-Move chess) is a chess variant in which each player moves twice per turn. The rules of the game were first published in Marseillais local newspaper "Le Soleil" in 1925. The variant became quite popular in the late 1930s with such chess grandmasters as Alexander Alekhine, Richard Réti, Eugene Znosko-Borovsky, and André Chéron playing it.
Rules.
A player can either move one piece twice or move two different pieces on his turn. Castling is considered a single move.
When a player gives check on the first move, he loses the second move of his turn. If a player is in check, he must move out of check on the first move of the turn. It is not allowed to move the king into check on the first move of a turn and then move out of check on the second. 
"En passant" capture is allowed even if the opponent moved the corresponding pawn on the first move of their turn. Capturing "en passant", however, must be done on the first move of the turn. When "two" pawns can be captured "en passant", both can be captured in the turn. 
To ensure White's advantage of moving first is not excessive, usually a "balanced" version of the game is played. In the balanced version, White makes only "one" move on the first turn. The moves are made in the following order: "White, Black, Black, White, White, Black, Black," and so on. This rule was introduced in 1963 by Robert Bruce and has gained wide acceptance since then.
References.
Bibliography