



160 



STEKILITY FROM 



Chap. XVIII. 



depends mor 



on the constitution of 



than 





nature of the change; for certain whole groups 

 more than others ; 



affected 

 but exceptions always occur, for some species 



in the most fertile groups refuse to breed, and some in the 

 sterile groups breed freely. Those animals which usually breed 

 freely under confinement, rarely breed, as I was assured, in the 

 Zoological Gardens, within a year or two after their first import- 

 ation. When an animal which is generally sterile under 

 finement happens to breed, the young apparently do not in 

 this power ; for had this been the case, various quadrupeds 



con- 



birds 



hich ' are valuable for exhibition, would h 



bee 



ome 



common 



Dr. Br 



farms 63 that many animals in the 



Jardin des Plantes, after having produced young for three or 



four successive generations, become 

 result of too close interbreeding. 



but this may be the 



It is a remarkable 



stance that many mammals and birds 

 under confinement quite as readily a 

 than, they have procreated their own I 



produced hybrids 

 jven more readily 

 Of this fact many 



instances have been given ; 64 and we are thus reminded of 

 plants which when cultivated refuse to be fertilised by thei 

 pollen, but can easily be fertilised by that of a distinct species 



Finally 



changed conditions 

 injuriously on the reproduct 



conclude, limited as the conclusion is, that 

 of life have an especial power 



of acting 



ystem 



The whole case is 



quite peculiar, for these organs, though not diseased, are thus 



rendered incapable of performing their proper functions 

 form them imperfectly. 



Sterility of Domesticated Animals from changed conditions. — With respect 



to domesticated animals, as their domestication mainly depends on the 

 accident of their breeding freely under captivity, we ought not to expect 

 that their reproductive system would be affected by any moderate degree 

 of change. Those orders of quadrupeds and birds, of which the wild 

 species breed most readily in our menageries, have afforded us the greatest 

 number of domesticated productions. Savages in most parts of the world 

 are fond of taming animals ; 65 and if any of these regularly produced 



63 ' Journal de Physiologie,' torn. ii. 



p. 347. 



64 For additional evidence on this 



subject, see F. Cuvier, in ' Annales du 

 Museum,' torn. xii. p. 119. 



65 Numerous instances could be given. 

 Thus Livingstone (' Travels,' p. 217; 

 states that the King of the Barotse, 

 an inland tribe which never had any 

 communication with white men, *» 









