22 
Willis . — The Evolution of Species in Ceylon , 
not appear to die out except by accident. A very small accident may 
kill out a species while at or below the stage represented in the Ceylon 
classification by VR, whilst it will need a geological submergence or some 
such accident to kill out one represented by VC. 
Whether under exactly equal conditions of age, attachment to other 
areas, and favourable climates, &c., a tropical area would have more species 
than one in the temperate zone of equal size must remain an unsettled 
question. Most of the evidence on which we have relied for an affirmative 
answer must now be regarded as incapable of bearing such a load, and the 
rich floras of South Africa and West Australia contradict the assumption. 
As yet we know of nothing that can be adduced as a reason why almost 
limitless species should not survive on an area with reasonably good 
climatic conditions. There is no evidence whatever that any of the angio- 
spermous species of the Ceylon flora are dying out, and from analogy 
we may imagine this to be generally true. 
Summary. 
The paper is a continuation of previous papers in which, among other 
things, I have sought to show that Natural Selection has but little to do 
with the geographical distribution of species or the areas they occupy, and 
that the area occupied at any given time in any given country depends 
mainly upon the age of a species in that country (not its absolute age). 
The figures of rarity of the Ceylon flora, derived from the statistics 
extracted from Trimen’s Flora of Ceylon, are considered, and it is shown 
in the first place that they are incontrovertible, being much too numerous 
and too well worked out. The rarity of the endemic species (in figures 
going from I, Very Common, to 6 , Very Rare) is 4-3 or very close to that 
figure (Table II), that of the species found also in Peninsular India is 3-5, 
and that of the species of wider distribution is 3-0. 
Not only do the grand totals show these figures, but they come out 
family by family. Natural Selection cannot produce a result like this, 
acting with equal pressure on every family, and I therefore attribute the 
distribution"of species (taking them in groups of twenty or more) to age. 
Many objections are being raised to these views. The first, that the 
endemic species are really the oldest and not the youngest, is easily 
disposed of by the consideration that they belong to the same genera. 
The second, a restatement of the contention of the supporters of Natural 
Selection, that they are local species developed to meet local needs or to 
suit local conditions, is met largely by an arithmetical argument. 
Not only is the rarity much the same in every family, but all families 
show some species under every head from Common to Very Rare, and in 
increasing numbers (Table III). This holds for all families with fourteen 
or more endemic species, and for all groups of families with fewer. The 
