Origin of Species Variorum

→ These same organs at first appear to 1866 1869

The electric organs 1859 1860 1861

These organs appear at first to 1872

→ fish, of which 1866 1869 1872

which 1859 1860 1861

→ other; but this is far from the case. 1866 1869 1872

other. 1859 1860 1861

→ now lost. 1866 1869 1872

lost. The presence of luminous organs in a few insects, belonging to different families and orders, offers a parallel case of difficulty. 1859 1860 1861

→ we 1866

more closely, we 1869 1872

→ the requisite nervous power 1866 1869

being supplied with nerves proceeding from different sources, 1872

→ (and this is perhaps the most important of all the differences) being supplied through different nerves from widely different sources. 1866

being supplied through different nerves from widely different sources, and this is perhaps the most important of all the differences. 1869

and this is perhaps the most important of all the differences. 1872

→ disappears, 1866 1869

of an organ, apparently the same, arising in several remotely allied species, disappears, 1872

→ fish. 1866

group of fishes. 1869

group of fishes. 1872

→These same organs at first appear to offer another and

even

far

more serious difficulty; for they occur in

only

....

about a dozen

fishes,

kinds

of →fish, of which several are widely remote in their affinities.

~~Generally~~

Generally

When

when

the same organ

appears

is found

in several members of the same class, especially if in members having very different habits of life, we may

generally attribute

attribute

its presence to inheritance from a common ancestor; and its absence in some of the members to

its

....

loss through disuse or natural selection.

But

So that,

if the electric organs had been inherited from

one

some one

ancient

progenitor

progenitor,

thus provided,

....

we might have expected that all electric fishes would have been specially related to each →other; but this is far from the case. Nor does geology at all lead to the belief that

formerly

....

most fishes

had

formerly possessed

electric organs, which

most of

....

their modified descendants have →now lost. But when we look

closer to

the

subject

subject,

→we find in the several fishes provided with electric

organs,

organs

that these are situated in different parts of the

body,—

body,—that

that they

they

differ in construction, as in the arrangement of the plates, and, according to Pacini, in the process or means by which the electricity is

excited—and

excited— and

excited,—and

lastly, in →the requisite nervous power →(and this is perhaps the most important of all the differences) being supplied through different nerves from widely different sources. Hence in the several

~~remotely allied~~

remotely allied

fishes furnished with electric organs, these cannot be considered as homologous, but only as analogous in function. Consequently there is no reason to suppose that they have been inherited from a common progenitor; for had this been the case they would have closely resembled each other in all respects. Thus the

~~greater~~

greater

difficulty →disappears, leaving only the lesser yet still great difficulty; namely, by what graduated steps these organs have

~~arisen and~~

arisen and

been developed in each separate → fish.