Origin of Species Variorum

→ OMIT 1872

the alimentary canal respires, digests, and excretes 1859 1860 1861 1866 1869

→ Cobites the alimentary canal respires, digests, and excretes. 1872

Cobites. 1859 1860 1861 1866 1869

→ the whole or part of an 1866 1869 1872

a part or 1859 1860 1861

→ OMIT 1869 1872

wholly change its nature 1859 1860 1861

greatly change its nature 1866

→ steps greatly change its nature. 1869 1872

steps. 1859 1860 1861 1866

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

Certain plants, as some Leguminosæ, Violaceæ, &c., bear two kinds of flowers; one having the normal structure of the order, the other kind being degraded, though sometimes more fertile than the perfect kind: if the plant ceased to bear its perfect flowers, and this did occur during several years with an imported specimen of Aspicarpa in France, a great and sudden transition would apparently be effected in the nature of the plant.

→ OMIT 1872

in some cases 1869

→ with comparative suddenness in 1872

in 1869

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

is a distinct question how 1866

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

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

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

individual sometimes perform simultaneously 1866

individual may simultaneously perform 1869

→ individual the same function, 1872

function, 1866 1869

→ OMIT 1869 1872

having a ductus pneumaticus for its supply and 1866

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

partitions. 1866

→ groups, 1869 1872

genera or families, 1866

→ might readily 1872

might with ease 1859 1860

might 1861

or means of performing the same function might 1866

for performing the same function might 1869

an organ common to all the members of a

large

....

class, for in this latter case the organ must have been

first

originally

formed at

an extremely

remote period, since which all the many members of the class have been developed; and in order to discover the early transitional grades through which the organ has passed, we should have to look to very ancient ancestral forms, long since become extinct.

We should be extremely cautious in concluding that an organ could not have been formed by transitional gradations of some kind. Numerous cases could be given amongst the lower animals of the same organ performing at the same time wholly distinct functions; thus →OMIT in the larva of the dragon-fly and in the fish →Cobites the alimentary canal respires, digests, and excretes. In the Hydra, the animal may be turned inside out, and the exterior surface will then digest and the stomach respire. In such cases natural selection might

easily

....

specialise, if any advantage were thus gained, →the whole or part of an organ, which had

performed

previously performed

two functions, for one function alone, and thus →OMIT by insensible →steps greatly change its nature. ↑ 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 →OMIT be effected →with comparative suddenness in the character of the species. It →is, however, probable that the two sorts of flowers borne by the same plant → were originally differentiated by finely graduated steps, which may still be followed in some few cases. Again, two distinct

organs

organs,

the same →organ under two very different forms, may simultaneously perform in the same →individual the same function, and this is

a highly

an extremely

important means of transition: to give one

instance,—there

instance,—

are

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 →OMIT being divided by highly vascular →partitions, and having a ductus pneumaticus for the supply of air. 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 →groups, but some few

plants

species

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 →might readily be modified and perfected so as to perform all the

work

work,