Origin of Species Variorum

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

Many cases are known of plants which regularly produce at different parts of 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.

→ might 1861

might with ease 1859 1860

or means of performing the same function might 1866

for performing the same function might 1869

might readily 1872

→ fish, or, for I do not know which view is now generally held, a part of the auditory apparatus has been worked in as a complement to the swimbladder. 1859 1860 1861 1866

fish. 1869

fishes. 1872

→ seems to me to be no extreme difficulty in believing that natural selection 1861 1866

seems to me to be no great difficulty in believing that natural selection 1859 1860

is no reason to doubt that the swimbladder 1869 1872

→ converted a swimbladder into a 1859 1860 1861 1866

been converted into 1869 1872

→ On this view it may be inferred 1861 1866

I can, indeed, hardly doubt 1859 1860

According to this view it may be inferred 1869 1872

→ prototype, of which we know nothing, 1859 1860 1861 1866

and unknown prototype, which was 1869 1872

nature of the plant. ↑ Two distinct organs sometimes perform simultaneously the same function in the same individual; to give one instance, there 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. In

all such

these

cases,

cases

one of the two organs →might be modified and perfected so as to perform all the

work,

work

~~by itself,~~

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

wholly

quite

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

pur- pose,

purpose,

namely,

namely

flotation, may be converted into one for a

widely

wholly

different purpose,

namely,

namely

respiration. The

swimbladder

swim-bladder

has, also, been worked in as an accessory to the auditory organs of certain →fish, or, for I do not know which view is now generally held, a part of the auditory apparatus has been worked in as a complement to the swimbladder. All physiologists admit that the

swimbladder

swim-bladder

is homologous, or "ideally

similar,"

similar"

in position and structure with the lungs of the higher vertebrate animals: hence there →seems to me to be no extreme difficulty in believing that natural selection has actually →converted a swimbladder into a

lungs,

lung,

an organ

organ

used exclusively for respiration.