104 J. MURRAY 



can scarcely be effected by any other agency than the winds. The prevalent storm 

 winds on the Antarctic coast are southerly. The Tardigrada of the different regions 

 do not correspond more closely with the nearest northern lands than with other 

 regions, except to some small extent to the south of Cape Horn, where access to the 

 Antarctic from the north is easiest. In Victoria Land all the species of Tardigrada 

 yet found are unknown in New Zealand, with the one exception of D. alpinum, and 

 M. furciger, an Antarctic species found in New Zealand, is absent from Victoria 

 Land. 



Undoubtedly migration along the Antarctic coast is easier than migration to it 

 from the north. In that case the birds, such as the Skua gulls, could assist in the 

 process. If the Antarctic has been peopled from the north, the Cape Horn to 

 Graham Land route is the likeliest to have been followed, and the numerous islands 

 would make it easier. 



There is little evidence that any species have been developed through long 

 isolation in the Antarctic. M. furciger and M. asper might have originated thus 

 and spread to the north, but it is quite as likely to have been the other way round. 

 There are, of course, the three species peculiar to the Antarctic, but they may any 

 day be found on the other side of the world, as happened with M. antarcticus. 



Contrasting the Antarctic Tardigrada with the Rotifera of the same region, we 

 arrive at the following considerations. In both groups there are about the same 

 number of Antarctic species known. In the Tardigrada the few peculiar species are 

 not very peculiar, and their modifications do not appear to render them better fitted 

 for the conditions than other species. None of them is strikingly abundant in the 

 region. If there is a dominant species in any region it is M. arcticus. The peculiar 

 species of Bdelloid Rotifera are more peculiar, and their peculiarities seem more 

 likely to have arisen through long isolation, in adaptation to the conditions, and the 

 extraordinary abundance of some of them (e.g., Philodina gregaria and Adineta 

 grandis] bear this out. 



The different life-conditions of these two groups must, however, be borne in mind. 

 The Bdelloids reproduce only parthenogenetically, so that there is no check by cross- 

 breeding to variation. The Tardigrada are sexual, so that if fresh migrants arrived, 

 even at long intervals, the development of new forms would be retarded. 



One of the most curious features in the Antarctic Tardigrade fauna is the absence 

 of the genus Echiniscus from the Antarctic Continent. No Echiniscus is yet known 

 on the continent, or anywhere south of the Antarctic Circle. In the North Polar 

 region there are at least a dozen species found within the Arctic Circle, and almost as 

 many even in Spitsbergen and Franz- Josef Land, in latitude 80 or higher. Is it 

 that the Ecliinisci are less resistant to cold than the Macrobioti 1 In the Antarctic 

 Islands, the South Orkneys and South Shetlands, &c., there are many species of 

 JEchiniscus. 



The relation of the Antarctic Tardigrade fauna to that of other regions of the 



