pparently sound, we must admit the Pallasian doctrine that long-continued
domestication tends to eliminate that sterility which is natural to species
when crossed in their aboriginal state.

{111}

_On increased Fertility from Domestication and Cultivation._

Increased fertility from domestication, without any reference to crossing,
may be here briefly considered. This subject bears indirectly on two or
three points connected with the modification of organic beings. As Buffon
long ago remarked,[242] domestic animals breed oftener in the year and
produce more young at a birth than wild animals of the same species; they,
also, sometimes breed at an earlier age. The case would hardly have
deserved further notice, had not some authors lately attempted to show that
fertility increases and decreases in an inverse ratio with the amount of
food. This strange doctrine has apparently arisen from individual animals
when supplied with an inordinate quantity of food, and from plants of many
kinds when grown on excessively rich soil, as on a dunghill, becoming
sterile; but to this latter point I shall have occasion presently to
return. With hardly an exception, our domesticated animals, which have long
been habituated to a regular and copious supply of food, without the labour
of searching for it, are more fertile than the corresponding wild animals.
It is notorious how frequently cats and dogs breed, and how many young they
produce at a birth. The wild rabbit is said generally to breed four times
yearly, and to produce from four to eight young; the tame rabbit breeds six
or seven times yearly, and produces from four to eleven young. The ferret,
though generally so closely confined, is more prolific than its supposed
wild prototype. The wild sow is remarkably prolific, for she often breeds
twice in the year, and produces from four to eight and sometimes even
twelve young at a birth; but the domestic sow regularly breeds twice a
year, and would breed oftener if permitted; and a sow that produces less
than eight at a birth "is worth little, and the sooner she is fattened for
the butcher the better." The amount of food affects the fertility even of
the same individual: thus sheep, which on mountains never produce more than
one lamb at a birth, when brought {112} down to lowland pastures frequently
bear twins. This difference apparently is not due to the cold of the higher
land, for sheep and other domestic animals are said to be extreme