and distribution of plants and animals. Most likely the West Antarctic 

 bridge was sunk during the final upheaval of the Cordillera and the 

 definite cooling of the Polar zone. The connections Enderby-Kerguelen 

 and East Antarctica - Tasmania and New Zealand are more hypothetical, 

 but we cannot explain the biogeography of the subantarctic zone without 

 them. 



Summary of Discussion 



Dr. Yonge suggested that the differences pointed out between the 

 Arctic and Antarctic flora in numbers of endemics, might be explained 

 by the fact that Antarctica was itself a continent, while towards the 

 Arctic the northernmost parts of the great continents continue upward. 



Dr. Falla wondered whether the tolerances and physical needs of 

 Macrocystis were sufficiently narrow to make it a useful indicator genus, 

 as proposed by Dr. Skottsberg. It did not occur, it was answered, in 

 the true antarctic. Dr. Deacon stated he had found it in the South 

 Orkney Islands, and Dr. Skottsberg replied that this was a possibility 

 which would prove very interesting. It was present certainly in South 

 Georgia, but was very small compared with its occurrence at Kerguelen 

 and the Falkland Islands in such thick belts that there was no chance 

 of getting ashore. 



Miss Moore pointed out that New Zealand lay across the subtropical 

 convergence. Many algas, including Macrocystis, reach their limit 

 on the North Island coasts, serving to mark diagrammatically the margin 

 of the convergence zone. Desmarestia was another case in point. Some 

 northern species, especially on the east coast, are observed to overlap to 

 the south. The Tasmanian algal flora agrees much more closely with 

 our New Zealand North Island than with the South Island flora. This 

 serves again to confirm the inclusion of Tasmania and the North Island 

 of New Zealand within the subtropical convergence. 



Professor Chapman raised some further problems which he considered 

 were opened up by Skottsberg's paper. On Wegener's Theory of Contin- 

 ental Drift he (Professor Chapman) and Dr. Skottsberg did not see eye 

 to eye. Professor Chapman still adhered to the continental drift ideas, 

 and had heard no evidence from Dr. Skottsberg's paper to confute that 

 •view. Dr. Skottsberg, in discussing the origin of cold-water alg£e, had 

 claimed that a point must have been reached in the Tertiary where 

 there was no cold water at all. But to-day, even in subtropical South 

 Africa and California, we do get cold water weUing up. The algae may 

 have evolved in the pre-glacial period and survived in these masses of 

 cold water. Antarctic mud had been shown to underlie the diatomaceous 

 ooze, and if Dr. Skottsberg was correct in thinking that the waters were 

 warmer it would be likely that a further deposit of diatomaceous ooze 

 would underlie the mud. Dr. Skottsberg, in replying, did not under- 

 rate the importance of the upwelling of colder waters, but pointed out 

 that each such up-flow must have an original source, which is to-day 

 the Polar ice-cap. No such sources could have existed during the early 

 Tertiary. He agreed, however, that it was hardly possible that the 

 subantarctic cold-water species could have evolved after the Tertiary 

 glaciation. Professor Chapman wondered if the oceanographers could 

 render assistance with the question of past cold-water occurrences. 

 Dr. Deacon thought that little attention had yet been given to the 

 problem raised. 



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