Origin of Species Variorum

↑ 1 blocks not present in 1859 1860 1861 1866; present in 1869 1872

Many plants are known which regularly produce at the same time differently constructed flowers; and if such plants were to produce one kind alone, a great change would in some cases be effected in the character of the species.

→ is a distinct question how 1866

can also be shown that the production of the two sorts of flowers by 1869

is, however, probable that the two sorts of flowers borne by 1872

→ has come to produce two kinds of flowers; but it can be shown in some cases to be probable, and in other cases to be almost certain, that this has been effected by finely graduated steps. 1866

has been effected by finely graduated steps. 1869

were originally differentiated by finely graduated steps, which may still be followed in some few cases. 1872

→ individual sometimes perform simultaneously 1866

individual may simultaneously perform 1869

organ under two very different forms, may simultaneously perform in 1872

→ function, 1866 1869

individual the same function, 1872

→ having a ductus pneumaticus for its supply and 1866

OMIT 1869 1872

→ partitions. 1866

partitions, and having a ductus pneumaticus for the supply of air. 1869 1872

→ genera or families, 1866

groups, 1869 1872

→ or means of performing the same function might 1866

might with ease 1859 1860

might 1861

for performing the same function might 1869

might readily 1872

their inflorescence, as on the summit of a spike and lower down, or at the centre and circumference of an umbel, corymb, &c., or during different periods of the year, differently constructed flowers; and if the plant were to cease producing both kinds and bore one alone, a great change would suddenly be effected in its specific character. ↑ It →is a distinct question how the same plant →has come to produce two kinds of flowers; but it can be shown in some cases to be probable, and in other cases to be almost certain, that this has been effected by finely graduated steps. Again, two distinct

organs,

organs

the same →individual sometimes perform simultaneously the same →function, and this is

an extremely

a highly

important means of transition: to give one

instance,—

instance,—there

there are

are

fish with gills or branchiæ that breathe the air dissolved in the water, at the same time that they breathe free air in their swimbladders, this latter organ →having a ductus pneumaticus for its supply and being divided by highly vascular →partitions. To give another instance from the vegetable kingdom: plants climb by three distinct means, by spirally twining, by clasping a support with their sensitive tendrils, and by the emission of

aërial

rootlets; these three means are usually found in distinct →genera or families, but some few

species

plants

exhibit two of the means, or even all three, combined in the same individual. In

these

all such

cases,

cases

one of the two organs →or means of performing the same function might be modified and perfected so as to perform all the

work

work,

by itself,

....

being aided during the

progress

process

of modification by the other organ; and then this other organ might be modified for some other and quite distinct purpose, or be

quite

wholly

obliterated.

The illustration of the swimbladder in fishes is a good one, because it shows us clearly the highly important fact that an organ originally constructed for one

purpose,

pur- pose,