ECOLOGICAL 103 



the wild asses. All these trust to their swiftness and to their ability 

 to travel quickly for long distances. They have discovered the 

 nomad's solution — rapid trekking, away from drought, snowstorms, 

 and dust-storms, extreme frost, and other difficulties. They are less 

 secure, however, than the burrowers, and their numbers are declining, 

 especially on the European Steppe. The wild horse or Tarpan, 

 which was common when Brehm visited the Asiatic Steppes about 

 fifty years ago, is now unfortunately extinct. Very delightful is the 

 picture he gives of one of the wild asses, the Kiang or Kulan {Equus 

 hcBmionus), but it is almost confined to the lofty tablelands, to which 

 its exceptionally thick coat is well suited. 



There is a fourth contingent of mammals on the steppes — namely, 

 the beasts of prey, who levy toll on the herbivores, both large and 

 small. Such are the weasels and pole-cats, the wolves and foxes, 

 the badger and the glutton. But they are rather to be regarded as 

 raiders from the forest than as characteristic steppe mammals. 



What has been said of the mammals might be said, mutatis mu- 

 tandis, of the birds. The sand-martins may represent the burrowers; 

 the bustards, cranes, and quails correspond to the swift jerboas; the 

 rooks and bee-eaters follow the grazing herds ; the eagles and falcons, 

 the buzzards and harriers correspond to the beasts of prey. The 

 ocean of grass teems with vegetarian insects, such as locusts and 

 bugs; and these become re-incarnated in lizards and snakes, which 

 are at home on the steppes in large numbers and in great variety. 



Antarctic Animals. — In very cold weather our imaginings 

 always carry us to polar regions, or to snowclad mountains, or to the 

 eternal winter of the deep sea. There is some subtle reflex that makes 

 us conjure up environments which are colder than our own; and so 

 we often come to think of the Antarctic. As long as we keep to the 

 open sea and the deep waters, there is an undeniable parallelism 

 berween the fauna of the Far North and the fauna of the Far South ; 

 and this formed the basis of an almost obsolete "Bipolarity Theory", 

 which interpreted the similarity as dae to a common origin of polar 

 marine animals in early Tertiary times from a somewhat uniform 

 population in temperate and tropical seas. But there seems to be no 

 need for any special theory beyond the assumption that similarly 

 adapted types of life are likely to arise in or find their way to 

 similar haunts. 



While there are few cases of the same pelagic and abyssal species 

 occurring in Arctic and Antarctic seas, there is a general parallelism. 

 But this is not illustrated by the animals of the shore, and still less 

 by those on land. In fact, the contrast between terrestrial animals 

 in the Far North and in the Far South is very striking. Thus Bruce 

 of the Scotia, in his interesting lectures, used always to emphasise 

 four facts : that there were no land mammals in the Antarctic regions, 

 that there was only one kind of land bird (the sheath-bill), that there 



