Chap. XVIII. CHANGED CONDITIONS. 145 



breeding as freely as the common kinds within a year after their 

 importation from the upper Nile. The guinea-fowl, an aboriginal 

 of the hot and dry deserts of Africa, whilst living under our damp 

 and cool climate, produces a large supply of eggs. 



Nevertheless, our domesticated animals under new conditions 

 occasionally show signs of lessened fertility. Roulin asserts that 

 in the hot valleys of the equatorial Cordillera sheep are not fully 

 fecund;' and according to Lord Somerville, 71 the merino-sheep 

 which he imported from Spain were not at first perfectly fertile. It 

 is said 72 that mares brought up on dry food in the stable, and 

 turned out to grass, do not at first breed. The peahen, as we have 

 seen, is said not to lay so many eggs in England as in India. It 

 was long before the canary-bird was fully fertile, and even now first- 

 rate breeding birds are not common. 73 In the hot and dry province 

 of Delhi, as I hear from Dr. Falconer, the eggs of the turkey, 

 though placed under a hen, are extremely liable to fail. According 

 to Roulin, geese taken to the lofty plateau of Bogota, at first laid 

 seldom, and then only a few eggs ; of these scarcely a fourth were 

 hatched, and half the joung birds died ; in the second generation 

 they were more fertile; and when Roulin wrote they were becoming 

 as fertile as our geese in Europe. With respect to the valley of 

 Quito, Mr. Orton says : 74 " the only geese in the valley are a few 

 imported from Europe, and these refuse to propagate." In the 

 Philippine Archipelago the goose, it is asserted, will not breed or even 

 lay eggs. 76 A more curious case is that of the fowl, which, accord- 

 ing to Roulin, when first introduced would not breed at Cusco in 

 Bolivia, but subsequently became quite fertile ; and the English Game 

 fowl, lately introduced, had not as yet arrived at its full fertility, 

 for to raise two or three chickens trom a nest of eggs w r as thought 

 fortunate. In Europe close confinement has a marked effect on the 

 fertility of the fowl : it has been found in France that with fowls 

 allowed considerable freedom only twenty per cent, of the eggs failed ; 

 when allowed less freedom forty per cent, failed; and in close con- 

 finement sixty out of the hundred were not hatched. 76 So we see that 

 unnatural and changed conditions of life produce some effect on the 

 fertility of our most thoroughly domesticated animals, in the same 

 manner, though in a far less degree, as with captive wild animals. 



It is by no means rare to find certain males and females which will 

 not breed together, though both are known to be perfectly fertile 

 with other males and females. We have no reason to suppose that 

 this is caused by these animals having been subjected to any change 

 in their habits of life ; therefore such cases are hardly related to our 

 present subject. The cause apparently lies in an innate sexual in- 



70 " Mem. par divers Savans," 'Acad. 74 'The Andes and the Amazon,' 

 des Sciences,' torn, vi., 1836, p. 347. 1870, p. 107. 



71 Youatt on Sheep, p. 181. 7S Grawfurd's ' Descriptive Diet, of 



72 J. Mills, 'Treatise on Gattle,' the Indian Islands,' 1856, p. 145. 

 1776, p. 72. ■» < Bull, de la Soc. d'Acclimat.,* 



73 Bechstein, ' Stubenvogel,' s. 24'-*. torn ix., 1862, pp. 380, 384. 

 VOL. II. L 



