Willis. — The Distribution of Species in New Zealand. 457 
of that species within that country (the species being taken in groups of 
twenty or so) ; and it affords striking confirmation of that hypothesis. 
Starting from the hypothesis, numerous predictions were made as to 
the phenomena which should be expected to be shown by the flora of New 
Zealand, and as all these predictions were borne out by the facts, several 
new discoveries were thus made as to the geographical distribution of plants 
in those islands. 
For example, it was predicted that if New Zealand were divided into 
zones of 100 miles in width, the number of endemic species would be com- 
paratively small in the outer zones and would increase steadily towards 
some central point (or points). This proved to be the case, not only with 
the whole flora but with all the single families and genera (Tables II I— VI)» 
It was further predicted and verified that the range of an endemic species 
would on the average be greater the nearer that one of its limits was to 
either end of the islands, the facts showing (Table VII) that the range varied 
down from 691 miles to 272, and then up again to 753. 
Other predictions made and verified were that the wides and endemics 
would be arranged in graduated series as in Ceylon, the former much the 
commoner and most numerous at the top of the scale, the latter at the 
bottom, not only on the total but in the families and genera (Tables VIII- 
XII) ; that both wides and endemics would show comparatively few in the 
early or lower stages of the scale, and greater crowding higher up ; that the 
average area occupied in New Zealand by a species would be much greater 
than in Ceylon ; and finally that both wides and endemics would have gone 
farther up the scale, and that a larger proportion would occupy all the 
available area. 
Very strong evidence is thus adduced in favour of the hypothesis of age 
and area, and in any case, whether it be accepted or not, it is clear that the 
distribution of plants follows simple arithmetical rules, and is probably 
a sequel of evolution, not a phenomenon thereof. 
I 1 2 
