ANTARCTIC ROTIFERA 63 



to decide whether the advance of knowledge will be better served by emphasising the 

 affinities in using the old names or pointing the differences in bestowing new names. 



If the rotifers are not aboriginal but have reached the Antarctic by immigration 

 in comparatively recent times, since the last period in which the conditions were such 

 as to prevent the continuance of life on the continent, we must look for some possible 

 means of immigration. 



The Rotifera share with the lowest forms of life that facility for distribution 

 which makes them, as Jennings (21) puts it, "potentially cosmopolitan." The agent 

 of distribution is the wind. When some rotifers, and the eggs of others, are dried they 

 may be blown in the form of dust for long distances. There is no difficulty in 

 supposing the Antarctic peopled in this way, though there is no region where such 

 distances of sea must be crossed in the process ; but all round the Antarctic continent 

 the storm-winds generally blow off the land, and so could play no part in bringing a 

 rotifer population to the country. 



There are numerous small islands scattered over the Antarctic Ocean, and there 

 are some storms which blow from the north : even in the Antarctic they are known, 

 though rare. While it is difficult to believe the wind currents of the lowest strata 

 of the atmosphere adequate to transport rotifers over the wide ocean separating, for 

 example, New Zealand and South Victoria Land, they might transport them from one 

 island to another, and thus the rotifers might in long ages work their way by slow 

 and intermittent steps from the one land to the other. 



There is yet another way in which the wind might be supposed to effect the 

 transference. If a violent local storm were capable of whirling rotifer dust up till it 

 was caught in those high currents which set to the southward, then they might 

 conceivably be carried all the way and dropped on land. If, however, it were as easy 

 as all that, we would expect a much more extensive rotifer fauna. 



In one region, south of Cape Horn, the Antarctic continent approaches very near 

 one of the other continents, and there the rotifer dust might readily be blown across. 

 From such a point of easy access the animals might get distributed all round the 

 Antarctic coast by the aid of wind and birds. 



The paucity of the rotifer fauna, as far as we know it, points to great difficulty of 

 access. The varying degrees of peculiarity exhibited by the different species suggest 

 that some have been longer resident in the Antarctic than others. Hydatina senta 

 may be a recent immigrant, may even have taken passage with Captain Scott in the 

 early days of the present century : Callidina habita and C. angularism&y have been 

 there for a few hundreds or thousands of years : whilst Philodina alata, P. gregaria 

 and Adineta grandis may be aborigines of immense antiquity. 



That great difficulties lie in the way of emigration to the Antarctic, and 

 difficulties quite apart from the climatic rigours which meet the immigrants, we have 

 one more indication in the adaptability of many rotifers to various climates. Not 

 only do a grea.t many species extend from the temperate into the Arctic Region, but 



