338 SCIENCE PROGRESS 



Antarctic Continent in past times putting New Zealand, Tasmania, and South 

 America into communication, and permitting the interchange of inhabitants, has 

 received a great measure of support from the discoveries by recent South Polar 

 expeditions not only of continental and stratified rocks within the Antarctic circle, 

 but also of coal, proving that the climate in past times has permitted life to 

 flourish in these regions. These important discoveries afford a firm basis for the 

 students of geographical distribution who have been accumulating in recent years 

 a large body of evidence showing a striking community between the animals and 

 plants inhabiting the temperate countries of the southern hemisphere, which are 

 separated indeed to the east and west by wide and probably permanent oceans, 

 but which almost impinge towards the south upon the Antarctic Continent. It 

 must, however, be admitted that although all are agreed, both zoologists and 

 botanists, as to the fact of Southern Australia, New Zealand, and South America 

 having a considerable common element in their fauna and flora, yet there is 

 considerable diversity of opinion as to whether this community necessarily implies 

 a land connection across the Antartic Continent. The great majority of zoologists, 

 including practically all those who have personally investigated the matter, are 

 agreed that whether an actual land connection existed or not, at any rate the 

 extension of land in the extreme southern hemisphere has been very much greater 

 in times past than it is now, and that various forms of land and fresh-water 

 animals have thus been enabled to pass, possibly by means of archipelagos of 

 islands, from one region to another, with far greater facility than is at present the 

 case. The botanists, however, are not agreed as to the necessity of taking 

 this view, and in the report before us we notice a considerable divergence 

 of view between Mr. Cheeseman and his zoological colleagues. The gist of 

 Mr. Cheeseman's argument appears to be that although certain of the same and 

 closely related species of plants exist in Fuegia, New Zealand, and Southern 

 Australia, yet there are many whole families of plants characteristic of the one 

 country entirely absent in the others, while many of the species that are common 

 to the three regions are plants with special means of dispersal which are found 

 all over the southern seas. He is therefore inclined to think that the dispersal 

 of these plants has taken place under conditions very similar to those now 

 existing, and that the radical differences in the flora of the southern continents 

 are not consistent with the existence of a large continental extension connecting 

 them together. 



The faciUty with which plant seeds are rapidly dispersed over wide areas, 

 despite barriers of mountains and seas, largely prohibits their use in the solution 

 of geographical problems. It would appear that the determining factor for plant 

 distribution is not so much the existence of continuous land, but rather the nature 

 of the physical conditions, and the existing plant-associations in the countries 

 to which they may be from time to time fairly universally dispersed, but in which 

 they fail to find a footing. In the case of land and fresh-water animals which 

 have not got special modes of dispersal, we are led to fall back upon a wider 

 extension of land surface to account for their wide and discontinuous distribution ; 

 but zoologists should admit that until a great deal more is known about the 

 possibility of dispersal across the sea, either by birds or in the water by currents, 

 it is not safe to dogmatise on these questions. We are in need of systematic and 

 careful e.xperimentation as to the means of dispersal of special groups of small 

 land and fresh-water invertebrates, concerning which very little is at present 

 known. This is certainly desirable ; but the systematic e.xploration of the habit- 

 able globe, and the careful description of its inhabitants, living and fossil, is an 



