80 . Proceedirigs. 



west coast, causing precipitation of their moisture on the west side, and gi-eat dryness 

 on the east. He also gave examples of the small amoiint of moistvu-e which the desert 

 plants lost by evaporation, and stated that, roughly speaking, about 220 species of 

 flowering-plants, found in the inland parts of the Island, belong to this category. He 

 argued that such a flora could not have arisen smce the Pleistocene epoch, but that it 

 was probably due to an intensification of the present conditions. An elevation of 5,000 ft. 

 of the central chain of the South Island witliin comparatively recent times would have 

 been accompanied on its eastern side by an extremely dry climate, tending to the produc- 

 tion and survival of a xerophytic flora. It would also serve to account for the glacial 

 phenomena now visible in many parts of the country, for the formation of the great 

 glacier-lakes, and of the West Coast Sounds, with their terminal moraines under the sea 

 outside their entrances. Summmg up all the evidence available from a consideration 

 of the existing flora of New Zealand, he pronounced strongly against the possibility of a 

 glacial epoch within recent geological times. 



Dr. Benham, treating the question from a biological point of view, said that tlie 

 question of a Pleistocene ice-sheet covering New Zealand, and continuous with the 

 extension of the polar ice-sheet, was one that had very important bearings on the 

 character of the fauna of these Islands, and any geological evidence there might be 

 which seemed to indicate the existence of such an ice-sheet must be correlated with 

 biological evidence. In the case' of the Northern Hemisphere the advance of the ice- 

 sheet forced existing life to migrate to tlie soiith, whence it retiirned on its withdrawal. 

 But here in the south there was no possibility of restocking the land after having been 

 covered by the ice-sheet. The fauna of New Zealand was in many respects of a remark- 

 able character owing to the great specialisation of its members ; yet it contained 

 descendants of ancestors which entered New Zealand at various periods from tlie north, 

 by way of New Guinea and other lands. Thus it was seen that at two periods New 

 Zealand was of much greater extent than at present — indeed, that it formed a small 

 continent, embracing New Caledonia, the Kermadecs, Chatham Islands, and the 

 Antarctic islands, though not necessarily at the same period. In this continental area 

 the descendants of the immigrants became specialised, and since the last period (Pliocene 

 at latest) there had been no communication with any other land. They knew approxi- 

 mately the date of separation of New Zealand from other land-svirfaces — in the latter 

 part of the Mesozoic period ; when it received many of its invertebrates — probably in the 

 early Pliocene, when it extended so far south as to include the Campbell, Auckland, 

 and Macquarie Islands, and received its southern forms from America, by way of an 

 Antarctic continent. It appeared that Cook Strait was formed in the later Pliocene ; 

 hence the faima of the South Island had ever since that period been isolated from that 

 of the North Island. A mere examination of the differences in the fauna of the two 

 Islands — quite apart from geological evidence — would indicate that the separation had 

 been longer than the Pleistocene, for a considerable period of time was necessary for the 

 evohition of species. Taking as an analogy Britain, which retained its land connection 

 with Europe till after the Ice Age, they saw tliat in Britain the species were practically 

 all identical with those of Europe ; but in New Zealand many of the birds were 

 represented by distinct species in the North and South Islands — as, for instance, the 

 Maori hen, which had one species in the North Island and three in the South Island ; 

 Notornis, which had one species m each Island ; the moas, which existed down to historic 

 times, had four different species, and even different genera, in the two Islands ; and the 

 parrakeet, crow, thrush, robm, tomtit, and weka each had distinct species in each Island. 

 As regarded snails, slugs, and other invertebrates, the same was the case, though they 

 lacked sufficient detailed knowledge to allow of statistics being presented. These differ- 

 ences imply a separation. Bi;t if the South Island were covered by an ice-sheet when the 

 northern limit extended to Cook Strait (vide Bulletin, p. 40), all the animals of the South 

 Island must have been wiped out. Whence did the present fauna, then, arrive ? Birds, 

 it will be said, can fly over Cook Strait. True ; but there will have been insufficient 

 time for the differentiation of species. But such an explanation is impossible in the 

 case of the snails, worms, spiders, and flightless insects such as the weta : these all re- 

 quired land connection. The earthworms of the South Island could not have been derived 

 from those of the North Island. Perhaps Professor Park would reply that the ice-sheet 

 left part of Marlborough uncovered ; but, even if Cook Strait were not as yet in exist- 

 ence, we still lacked sufficient time for the differentiation of species in the two Islands. 

 Moreover, the genera of earthworms were so greatly different tliat much longer time was 

 necessary. But a still more serious difficulty was incurred wlien they bore in mind that 

 this Pleistocene ice-sheet " was an extension of the polar ice-sheet " (p. 43). This polar 

 ice-sheet must have covered Campbell and Auckland Islands — as he himself believed to 

 have been the case — for at this time the elevation of the land in the early Pliocene placed 

 these islands m connection with the South Island of New Zealand. This ice-sheet must 



