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Species and other Controversial Points . 
occupy each one restricted locality. Polyalthia Korinti , Garcinia spicata , 
Impatiens oppositifolia , and forty other species common only to Ceylon and 
Peninsular India (often only a small southern part of it), and whose absolute 
range is thus small, presumably indicating age, are yet very common (and 
therefore presumably very young?) in Ceylon. Eugenia rotundifolia 
(endemic) is very common in Ceylon, and thirteen other endemic Eugenias 
are very rare. Are the latter very old, the former very young ? ’ 
‘ The hypothesis of youth and area, when the youth is to be absolute 
youth, cannot be established without calling in Natural Selection of a some- 
what remarkable kind. But as I have already pointed out (6, pp. 6 -t 6), 
Natural Selection must explain the very difficult problem, why every family 
and genus, in New Zealand as well as Ceylon, shows similar arithmetical 
arrangement of its species according to the area they occupy. 
‘ We are thus driven to accept the youth hypothesis in the form that it 
is youth within the country, or exactly to reverse my hypothesis of age and 
area. But if we do so accept it, we are at once brought up short by the 
question why ? What conceivable reason can be given to explain why the 
two things should be connected ? The case of the rapid spread of introduced 
weeds in islands like Ceylon or New Zealand is often quoted as evidence that 
foreign species recently introduced spread more rapidly than the local, but 
ignores three important facts at least : (i) that foreign conditions have also 
been introduced, e. g. by cutting down of forest, or in other ways ; (2) that 
such weeds are also common in continental areas, as for example at Rio de 
Janeiro, where the local flora of 7,000-8,000 species is one of the very richest 
in the whole world, and includes a vast number of species covering enormous 
areas of distribution, so that its members should be well able to hold their 
own, and (3) that where they have spread, it has been just as much at the 
expense of the wides already in the country as of the endemics. 
‘ To return to the main argument, why should a species which is very 
old (and therefore on this hypothesis very rare) in, let us say, South India, at 
once spread over a large area if it arrive in Ceylon ? Or, to take a concrete 
case, suppose that Coleus elongatus , which at present is confined to the 
summit of Ritigala ( 9 ) in Ceylon, and shows no signs of spreading thence, 
occurred not on Ritigala, but on one of the hills of South India. Would it 
at once spread if brought into Ceylon, and if not, why not ? Has it at one 
time existed all over Ceylon, and is the soil of that country now permanently 
Coleus elongatus-sick ? Or take it the other way : if carried from Ceylon 
to South India, would it at once spread? If not, why not?’ 
Mr. Ridley prefers to consider the endemics as the oldest species 
in a country. But he must in any case admit that the species confined 
to Ceylon and Peninsular India, which are intermediate, in area occupied, 
between the endemics and the wides, are intermediate also in age. We are 
p 
