Willis. — The Distribution of Species in New Zealand . 455 
from 1 to 10, is 6*5. The sixth class of New Zealand plants contains those 
with a range of 401-520 miles, or double the whole area of Ceylon. The 
average area occupied by an endemic in Ceylon is a circle of about 40 miles 
in diameter, so that it is at most about one-tenth of that occupied by an 
endemic in New Zealand. Even the lowest class of New Zealand endemics 
occupies, in the case of some of its members, as much room as this. 
This difference in area occupied by endemic species in the two islands 
is a very awkward point to explain on the theory of natural selection. 
New Zealand is quite as mountainous and varied as Ceylon, if not more so, 
yet its endemics occupy much more space. Few of them are, as in Ceylon, 
confined to one mountain (4*4 per cent, against 8-4 per cent.), though many 
occupy a whole range 30-40 miles long. 
If, as is further probable, the land connexion to New Zealand not only 
ended sooner, but began sooner than that to Ceylon, we shall expect to find 
that both wides and endemics have on the average gone farther up the scale, 
and that a larger proportion have occupied the whole available area. 1 
What has already been said, with a glance at the figures in the top class, is 
sufficient to show that this prediction also is borne out by the facts. 
Turning again to Table VIII, let us examine it more carefully. It will 
be noticed that the endemics increase in number with remarkable regularity, 
except at class 6, where the number 105 is intercalated between 79 and 97, 
and at the last two classes, where 128 and 168 follow immediately upon 93. 
The number 105 at class 6 seems to me a strong point in favour of my 
hypothesis, for in this class are included those endemics confined to one 
entire island only. Of these there are many, especially in the South Island, 
which has about 40 against about 6 in the North Island. The explanation 
appears obviously to be that most of them were held up, when they had 
reached the north end of the South Island, by the fact that that island was 
already separated from the North Island. One would therefore seem 
justified in subtracting from the number 105 a considerable number, 
perhaps 20 to 30, which would reduce it to a figure that would fit in very 
well with the figures for the classes above and below. It is worthy of note 
that of the 40 species mentioned, 10 are Veronicas, and 5 Celmisias. 
The sharp rise in the last two classes is probably to be explained by 
the fact that the earlier stages of spreading take much longer than the later. 
If these two classes were made into three, the numbers would progress as in 
the rest of the series. 
It is thus clearly evident that many predictions, based upon my hypo- 
thesis of c age and area are borne out by the actual facts in the most con- 
vincing manner. As in face of the facts that have been brought up natural 
selection is no longer tenable as an explanation of the geographical distri- 
1 The same thing might, of course, happen if New Zealand was less densely covered with 
cryptogamic vegetation, though the land connexion was not earlier. 
