Origin of Species Variorum

→ a whole group of species 1866 1869 1872

the species of a group 1859 1860 1861

→ OMIT 1869 1872

of a group of species 1859 1860 1861

of a group 1866

→ the early increase 1869 1872

increase 1859 1860 1861 1866

→ sudden. 1859 1860 1869 1872

sudden relatively to that of most other groups. 1861 1866

→ OMIT 1869 1872

whole subject of the 1859 1860 1861 1866

→ than I have done at the extinction of species. 1869 1872

at the extinction of species, than I have done. 1859 1860 1861 1866

→ OMIT 1869 1872

how utterly groundless was 1859 1860 1861 1866

→ astonishment was groundless. 1869 1872

astonishment! 1859 1860 1861 1866

final subsidence of an island, the process of extinction may have been rapid. Both single species and whole groups of species last for very unequal periods; some groups, as we have seen,

having

have

endured from the earliest known dawn of life to the present day; some

having

have

disappeared before the close of the palæozoic period. No fixed law seems to determine the length of time during which any single species or any single genus endures. There is reason to believe that the

complete

....

extinction of →a whole group of species is generally a slower process than their production: if

the

their

appearance and disappearance →OMIT be represented, as before, by a vertical line of varying thickness, the line is found to taper more gradually at its upper end, which marks the progress of extermination, than at its lower end, which marks the first appearance and →the early increase in

numbers

number

of the species. In some cases, however, the extermination of whole

groups

groups,

of beings,

....

as of

ammonites,

ammonites

towards the close of the secondary period, has been wonderfully →sudden.

The →OMIT extinction of species has been involved in the most gratuitous mystery. Some authors have even supposed

that

that,

as the individual has

definite length of life, so have species a definite duration. No one

I think

....

can have marvelled more →than I have done at the extinction of species. When I found in La Plata the tooth of a horse embedded with the remains of Mastodon, Megatherium, Toxodon, and other extinct monsters, which all co-existed with still living shells at a very late geological period, I was filled with astonishment;

for

for,

seeing that the horse, since its introduction by the Spaniards into South America, has run wild over the whole country and has increased in numbers at an unparalleled rate, I asked myself what could so recently have exterminated the former horse under conditions of life apparently so favourable. But →OMIT my →astonishment was groundless.

Professor

Pro- fessor