332 Dr. N. Severtzoft' on the Mammals of Turkestan. 



mens, the wild ones were also obliged to modify in order to 

 exist, and to avoid being driven altogether away by the tame 

 flocks, which were looked after and watched by men. 



0. arffoli has xerj coarse hair and soft underwool ; the 

 hair of the tame sheep is only moderately coarse ; and the 

 southern sheep do not possess any soft underhair at all. The 

 existence of this soft wool is to be regarded as a proof of 

 weakness, and is combined in the tame sheep with a com- 

 paratively much greater development of the organs of gene- 

 ration. Consequently it may be supposed that the weakest 

 and smallest sheep were selected for domestication ; and as 

 they easily got fat and bred quickest, they would also be 

 more likely to remain in a tame state, whilst the stronger 

 and wilder individuals would be apt to run away. The 

 increased development of fat and the organs of generation 

 may have been caused at first by the quiet life, and then in- 

 creased by artificial selection. With the wild sheep the oppo- 

 site would be the case ; for contest for the females would favour 

 the development of the horns and muscles rather than that 

 of the reproductive organs. In being driven out of the plains 

 by the tame herds of the nomad tribes, the weaker, smaller, 

 and less agile of the wild sheep would be killed in jumping 

 from rocks and ledges when pursued, especially in trying to 

 leap the ravines, over wliich the stronger leader of the flock 

 had shown the way ; or Avhen they lagged behind the flock 

 they would be killed either by the hunters or by beasts of prey ; 

 and in this way, through thousands of years perhaps, the 

 strongest sheep would continue to exist, whilst the weaker 

 ones with smaller horns were killed off. Such might be the 

 explanation of the difference in size between the wild and tame 

 sheep ; and it explains also their slower growth and deve- 

 lopment as well as their less prolificness. This process is 

 not merely hypothetical, but has its proofs in the skulls that 

 are found lying about on the rocks and in the ravines, most 

 of which belong to the weaker adult males. 



From the above considerations I am led to agree in Riip- 

 pell's opinion, that the fat-tailed sheep and 0. argali both 

 descend from one original stock, having undergone some 

 changes in opposite directions. The comparison of the wild 

 sheep also shows another characteristic, viz. that they are larger 

 in size and in their horns the higher the localities are which 

 they inhabit ; this can be traced from O. nigrimontana, through 

 0. Heinsii and O. Karelini^ up to O. Folii. In size the speci- 

 mens of O. Karelini that inhabit the Narin mountains are 

 hardly smaller than O. Polii^ judging by the skulls ; and the 

 0. Polii from the Aksay are probably the smallest represen- 



