with reference to the Dying Out of Species. 5 
a grave doubt as to the applicability of the theory in general, for there is 
not the least reason to suppose the Ceylon flora or the Ceylon conditions 
to be unique or isolated in any respect. 
The interpretation which I put upon the facts is simple. As all the 
plants, and all the families, behave alike, it is evident that their grouping 
and distribution must be the result of a cause which acts upon all with 
practically even pressure. Now Natural Selection could not do this, for 
in its essentials it is of a differentiating nature. The only cause that I can 
see which thus acts evenly upon all is age , and I am inclined, therefore, 
to think that the area occupied by any given species at any given time, 
in any given country, is to a large extent an indication of the age of that 
species in the country (not its absolute age, which has nothing to do with 
the question, so far as I can at present see). The widely distributed 
species, which must on the whole be the oldest, are the commonest, the 
Ceylon-Indian next oldest and next commonest, and the endemics, the 
youngest, are the rarest. In the case of a group of, say, twenty species 
of similar distributional origin, and the same family, as we have pointed 
out above, this is certainly extremely probable, but of course in the case 
of any single species numerous disturbing influences come into play. And 
it will be well to point out specifically that these remarks only apply as 
yet to the angiospermous species, and are based only on the flora of Ceylon, 
though the close similarity that I have observed at Rio de Janeiro leads 
me to believe that they apply generally to most floras. 
Still more true, in general, is this statement as regards those genera 
which contain a number of species, than as regards the actual species 
themselves. In two previous papers 1 I have gone into this question from 
the point of view of general geographical distribution, and may refer to 
them here. 
In other words, on the view of things thus propounded (which 
appears to me to have great probabilities in its favour, besides possessing 
the advantage of explaining numerous as yet unexplained facts in a simple 
way), endemic species confined to small areas are really species in the earlier 
stages of spreading , and, given time enough, they might ultimately be 
found covering large areas. Endemic species (all species are on this view 
endemic when young) begin as VR in some given country, and gradually 
extend their area, passing upwards through the stages R, RR, RC, &c. 
Already these views are meeting with numerous objections, and it will 
be well to deal with some of these in this paper. The first objection, that 
the endemic species are on the whole the oldest, and not, as I maintain, 
the youngest, is easily disposed of by a little consideration. Great numbers 
of well separated endemic species occur in such genera as Ranunctdus , 
1 The Geographical Distribution of the Dilleniaceae, as illustrating the treatment of this subject 
on the Theory of Mutation. Ann. Perad., vol. iv, 1907, p. 69; Phil. Trans., 1 . c., p. 335. 
