Chip. XVI. INCREASED FEETILITY FROM DOMESTICATION. Ill 



On increased Fertility from Domestication and Cultivation. 



Increased fertility from domestication, without any refer- 

 ence to crossing, may be here briefly considered. This subject 

 bears indirectly on two or three points connected with the mo- 

 dification of organic beings. As Buffon long ago remarked, 29 

 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 fertilitv 

 even of the same individual: thus sheep, which on mountains 

 never produce more than one lamb at a birth, when brought 



3 CJ 



» Quoted by Isid. Geoffrey St. the present subject has appeared in Mr. 



Hilairo, Hist Naturelle G^nerale,* Herbert Spencer's 'Principles of Bio- 



torn. m. p 4,6. Since this MS. has logy,' vol. ii, 1867, p. 457 et sea. 

 been sent to press a lull discussion on 



