90 



INCREASED FERTILITY 



Chap. XVI. 



breed four times yearly, and to produce each time at most 

 six young ; tlie tame rabbit breeds six or seven times yearly, 

 produc^'ng each time from four to eleven young ; and 

 Mr. Harrison AVeir tells me of a case of eighteen young 

 having been produced at a birth, all of which survived. 

 The ferret, though generally so closely confined, is more 

 prolific than its supposed wild prototype. The wild sow is 

 remarkaldy prolific; she often breeds twice in the year, and 

 bears from four to eight and sometimes even twelve young ; 

 but the domestic sow regularly breeds twice a j^ear, 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 of the same individual : thus sheep, which on moun- 

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

 brought down to lowland pastures frequently bear twins. 

 This difference apparently is not due to the cold of the higher 

 land, for !>heep and other domestic animals are said to be ex- 

 tremely prolific in Lapland. Hard living, also, retards the 

 period at which animals conceive ; for it has been found dis- 

 advantageous in the northern islands of Scotland to allow 

 cows to bear calves before the}^ are four years old.^^ 



Birds offer still better evidence of increased fertility from domesti- 

 cation : the hen of the wild (Julius binkiva lays from six to ten 

 eggs, a number which would be thought nothing of with the 

 domestic hen. The wild duck lays from live to ten eggs ; the tame 

 one in the course of the year from eighty to one hundred. The wild 

 grey-lag goose lays from five to eight eggs ; the tame from thirteen 

 to eighteen, and she lays a second time ; as Mr. Dixon has remarked, 

 " high-feeding, care, and moderate warmth induce a habit of proli- 

 ficacy which becomes in some measure hereditary." Whether the 

 semi-domesticated dovecot pigeon is more fertile than the wild 

 rock-pigeon, C. livia, I know not ; but the more thoroughly domesti- 



32 For cats and dogs, &c., see Bel- 

 lingeri, iu 'Annal. des Sc. Nat.,' 2nd 

 series, Zoolog., torn. xii. p. 155. For 

 ferrets, Bechstein, ' Naturgeschichte 

 Deutschlands,' Band i., 18i)l, s. 786, 

 795. For rabbits, ditto, s. 1123, 1131 ; 

 and Bronn's ' Geschichte der Natur.,' 

 B. ii. s, 99. For mountain sheep, 

 ditto, s. 102. For the fertility of the 



wild sow, see Bechstein's ' Naturgesch. 

 Deutschlands,' B. i., 1801, s. 534; for 

 the domestic pig, Sidney's edit, of 

 Youatt on the Pig, 1860, p. 62. With 

 respect to Lapland, see Acerbi's 

 'Travels to the North Cape,' Eng. 

 translat., vol. ii. p. 222. About the 

 Highland cows, see Hogg on Sheop, 

 p. 263. 



