The delineation of natural areas in New Zealand: Discussion

[First paragraph(s)...]
THE CHAIRMAN opening the discussion said the problem was to try to establish some community of pattern in the various ecological and biological factors present in the areas propounded as natural and see to what extent it was possible to make broad delineations of these areas Various points had emerged from the papers: the apparent significance of the 38th parallel; the effect of Cook Strait, which is a barrier to certain reptiles and some of the birds, but not to worms.
MR. DELL, answering a question on the discontinuous distribution of snails, said that some could be partly explained on the geo- logical evidence but the geologists' plans of the post-pliocene area in New Zealand were rather indefinite. If Wellman's theory of glaciation in New Zealand was accurate one had to envisage everything being pushed up from south to north by advancing ice, and subsequently the whole area being re-colonised and the forest advancing as the ice face disappeared and moved south; it was possible that some species found the only suitable conditions in the regenerating forest follow- ing on the disappearing ice sheet; certain of them perhaps stayed behind and adapted themselves and others carried on, following the retreating ice. For a long time it was believed that glaciation was the key to the distribution of Paryphanta, but if the geologists were right and the South Island was fairly devoid of this type of life it was a hard situation to envisage.