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become extinct ; for the common cattle, like horses, are able just to 
keep alive by browsing on the twigs of trees, and on reeds, with their 
lips. This the Niatas cannot so well do, as their lips do not join, and 
hence they are found to perish before the common cattle.”—{The 
Variation, vol. i., pp. QO-i.) 
It seems to me, then, that, on the whole, the Niata cattle 
do not afford a good illustration of the principle that 
changed conditions and their coadjutors could not have 
produced this conformation. The assertion that it is not 
always easy to say how far transforming influence and 
how far Natural Selection have co-operated to produce a 
given transmutation, has already been answered by the 
contention that the co-operation of the two processes is an 
impossible one. 
Having thus depreciated the transforming effects of 
changed conditions, Mr. Darwin proceeds to attribute the 
transmutation of species to Natural Selection only, and 
he takes for the special sphere of its operation the case of 
a confined and isolated area. 
“ In a confined or isolated area, if not very large, the organic and 
inorganic conditions of life will generally be almost uniform ; so that 
Natural Selection will tend to modify all the varying individuals 
of the same species in the same way.”—(Origin of Species, p. 81.) 
This illustration is an unfortunate one, because Mr. 
Darwin, on the very next page, gives a very good reason to 
show that such conditions would not be favourable to the 
action of Natural Selection. 
“ If, however, an isolated area be very small, . . . the total number 
of the inhabitants will be small, and this will retard the production of 
new species through Natural Selection by decreasing the chances of 
favourable variations arising.”—(Origin of Species, p. 82.) 
And therefore in this connection he admits the possibility 
of transformation apart from Natural Selection. 
“ In separated districts long continued exposure to different con 
ditions of life may produce new races without the aid of selection.” 
—( The Variation, vol. ii., p. 176.)