Origin of Species Variorum

→ nature of the seasons, 1872

seasons, 1859 1860 1861 1866 1869

→ As 1872

If I am right in believing that 1859 1860 1861 1866 1869

→ in such a manner that 1872

that 1859 1860 1861 1866 1869

→ take 1869 1872

in imagination adapt 1859 1860 1861 1866

→ it is a 1872

a 1859 1860 1861 1866 1869

→ OMIT 1872

as I believe, is 1859 1860 1861 1866 1869

→ OMIT 1869 1872

on my theory 1859 1860 1861 1866

of its range, where it exists in lessened numbers,

will

will,

during fluctuations in the number of its enemies or of its prey, or in the →nature of the seasons, be extremely liable to utter extermination; and thus its geographical range will come to be still more sharply defined.

→As allied or representative species, when inhabiting a continuous area, are generally

....

distributed →in such a manner that each has a wide range, with a comparatively narrow neutral territory between them, in which they become rather suddenly rarer and rarer; then, as varieties do not essentially differ from species, the same rule will probably apply to both; and if we →take a varying species

inhabiting

a very large area, we shall have to adapt two varieties to two large areas, and a third variety to a narrow intermediate zone. The intermediate variety, consequently, will exist in lesser numbers from inhabiting a narrow and lesser area; and practically, as far as I can make out, this rule holds good with varieties in a state of nature. I have met with striking instances of the rule in the case of varieties intermediate between well-marked varieties in the genus Balanus. And it would appear from information given me by Mr. Watson, Dr. Asa Gray, and Mr. Wollaston, that

generally

generally,

when varieties intermediate between two other forms occur, they are much rarer numerically than the forms which they

cannect.

connect.

Now, if we may trust these facts and inferences, and

therefore

....

conclude that varieties linking two other varieties together

have generally

generally have

existed in lesser numbers than the forms which they connect,

then,

then

I think,

....

we can understand why intermediate varieties should not endure for very long

periods;—

periods;—why,

periods:—

why

~~why,~~

why,

as a general

rule

rule,

they should be exterminated and disappear, sooner than the forms which they originally linked together.

For any form existing in lesser numbers would, as already remarked, run a greater chance of being exterminated than one existing in large numbers; and in this particular case the intermediate form would be eminently liable to the inroads of

closely allied

closely-allied

forms existing on both sides of it. But →it is a far more important consideration, →OMIT

that,

that

during the process of further modification, by which two varieties are supposed →OMIT to be converted and perfected into two distinct species, the two which exist in larger

numbers

numbers,

from inhabiting larger areas, will have a great advantage over the intermediate variety, which exists in smaller numbers in a narrow and intermediate zone. For forms existing in larger numbers will

always

....

have a better chance, within any given period, of presenting further favourable variations for natural selection to seize on, than will the rarer forms which exist in lesser numbers. Hence, the more common forms, in the race for life, will tend to beat and supplant the less common forms, for these will be more