Careful Words

survival (n.)

  The expression often used by Mr. Herbert Spencer of the Survival of the Fittest is more accurate, and is sometimes equally convenient.

Charles Darwin (1809-1882): The Origin of Species. Chap. iii.

  The Survival of the Fittest.

Herbert Spencer (1820-1903): Principles of Biology, Vol. i. Chap. xii. (American edition, 1867.)