ABSTRACT
This chapter presents an extract from an Unpublished Work on Species, by Charles Darwin, "On the Variation of Organic Beings in a State of Nature; on the Natural Means of Selection; on the Comparison of Domestic Races and True Species". Many practical illustrations of this rapid tendency to increase are on record, among which, during peculiar seasons, are the extraordinary numbers of certain animals; for instance, during the years 1826 to 1828, in La Plata, when from drought some millions of cattle perished, the whole country actually swarmed with mice. The chapter also presents an abstract of a letter from Darwin, to Prof. ASA Gray, Boston, US, Dated Down, September 5th, 1857. One of the strongest arguments which have been adduced to prove the original and permanent distinctness of species is that varieties produced in a state of domesticity are more or less unstable.
