Darwin and his generation were deeply imbued with the Butlerian tradition, and regarded the organic world as almost a miracle of adaptation, of the minute dovetailing of structure, function and environment.
Recent discoveries have shown that representatives of the two floras coexisted in certain regions; there was, in fact, a dovetailing between strata in Europe.
The hiatus is striking, but it cannot be held to necessitate an editorial dovetailing of two separate epistles.
