28 CONTACTS WITH DARWINISM II [ch. iii 



that overlap one another like the rings in a shirt of chain mail. 

 Now a little consideration will soon show that from the point of 

 view of evolution to suit local conditions this is a verv remarkable 

 state of affairs. If A and B grow in overlapping areas, both must 

 be growing in the coincident portion, and what keeps A from 

 growing into the rest of 5's territory, B into ^'s? In reality the 

 case is more complex, for if all the species were entered, there 

 would be. . .a dozen overlapping at any one point. It is all but 

 inconceivable that local adaptation should be so minute as this, 

 with soil essentially the same throughout, and the rainfall, etc. 

 varying much from year to year. The species would have to be 

 adapted to wide range in rainfall, and to very slight in a com- 

 bination of other factors. It was clear that the old ideas of 

 particular adaptation were quite untenable. 



Nor would the other popular theory, which equally survives 

 to-day, satisf}^ the knowledge that I now had about local distri- 

 bution. How could species be dying out in this remarkable chain- 

 mail pattern, and why were there so many with small areas? 

 Had one perhaps arrived in Ceylon just in time to see the 

 dying out of a considerable flora? And why did so many choose 

 mountain tops as a last resort? If they had climbed from below, 

 they must have plenty of adaptive capacity, and should be able 

 to compete with the new-comers. Still more, why did each one or 

 two choose a diff"erent mountain?. . .It was difficult to believe 

 that the plains were once inhabited by diff^erent species at every 

 few miles, whilst many mountains with endemics did not even 

 rise direct from the plains, but from a high plateau. 



Counting up all the species of the Ceylon flora, and dividing 

 them into three groups — those endemic to Ceylon, those found 

 onlv in Cevlon and South India, and those with a wider distribu- 

 tion abroad than this (which I termed zvides for short) — I found 

 (59) the endemics to be graduated downwards from few of 

 large distribution area to many of small (e.g. common 90, rare 

 192), and the wides in the other direction (e.g. common 462, 

 rare 159), with the Ceylon-South India species intermediate. In 

 other words, the average area occupied by an endemic was small, 

 that by a Cejdon-South India species larger, and that by a wide 

 the largest of all. A cursory examination of other floras showed 

 me that their endemic species also behaved in the same way, . . . 

 and I Avas at last furnished with what seemed to me to be a much 

 more feasible explanation of the distribution of species in general, 

 and endemics in particular. 



Having disposed, to my own satisfaction, of the notion that 

 endemics were moribund species, I adopted the view that in 

 Ceylon the mdes were the first species {o7i the whole'^) to arrive, 

 and had therefore on the whole occupied the largest areas. The 

 Ceylon-South India species, on my view, must have arisen from 



^ I.e. in any genus the wide would usually be the first to arrive. 



