DISTRIBUTION AND HABITS OF ARGALI SHEEP 155 



last there remained only isolated salt-lakes surrounded by 

 steppe -are as. 



Simultaneous with the desiccation of the salt-lakes the 

 periferical parts of the surrounding steppes began to lose 

 their moisture and vegetation, and parallel with this pro- 

 ceeded the invasion of sand. 



Thus the sand conquered greater and greater areas until 

 it finally covered the deserts that exist in our time. The 

 more abundant moisture in the mountains and on the high 

 plateaux could still allow the vegetation to thrive and 

 prevent further encroaching of the sand. 



That the marginal zones of the desert have not, until a 

 comparatively recent period, lost their moisture is proved 

 by the dried-up remains of forests which still are seen in 

 many localities of the Tarim Basin where — by the way — the 

 most striking proofs of the desiccation of Central Asia are 

 to be observed. 



On the steppe-areas which were formed after the 

 drying-up of the Han-hai there lived during the course of 

 time a number of animal species, several of which met their 

 fate and became extinct. This is testified by fossil remains 

 which have been found. These animals were in time suc- 

 ceeded by other species which were probably more suited 

 to the new climatological conditions and which were either 

 able to live on here or were ultimately forced to seek more 

 promising grounds in the mountains and high plateaux in 

 or at the desert. 



Whether we can count the Argali to this latter category 

 is a question which may be solved by fossil-hunting expedi- 

 tions in the steppes and deserts of Central Asia, But the 

 theory does not seem improbable. 



We may picture the various phases of the emigration 

 thus : During some of the earlier periods of desiccation, the 

 Argali lived scattered over certain parts of the vast steppe- 

 region; the grass was still abundant round the saltlakes. 

 The rivers and brooks from the mountain ranges still flowed 

 far out on the steppes. Springs and drinkable water still 

 existed in abundance along the margin of the steppe. 



The herds on one part of the steppe had connection with 

 flocks in other regions. 



But in the course of desiccation conditions changed. 

 The saltlakes and their surroundings lost moisture, the 

 steppe -regions became separated from each other by larger 

 and larger belts of barren ground. Where the lakes lay 

 comparatively close to each other the connection could still 

 be maintained. The Argali herds naturally sought their 



