several members of the same class, especially if in members having very different habits of life, we may
attribute | attribute 1859 1860 1861 1866 1869 | | generally attribute 1872 |
| its 1859 1860 1861 | its 1866 1869 1872 |
| But 1859 1860 1861 | | So that, 1866 1869 1872 |
| one 1859 1860 1861 | | some one 1866 1869 1872 |
| progenitor 1859 1860 1861 | | progenitor, 1866 1869 1872 |
| thus provided, 1859 1860 1861 | thus provided, 1866 1869 1872 |
| other. 1859 1860 1861 |
| other; but this is far from the case. 1866 1869 1872 |
| formerly 1859 1860 1861 | formerly 1866 1869 1872 |
| had 1859 1860 1861 | | formerly possessed 1866 1869 1872 |
| most of 1859 1860 1861 | most of 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 |
| now lost. 1866 1869 1872 |
| 4 blocks not present in 1859 1860 1861; present in 1866 1869 1872 | | But when we look closer to
the subject,
we
find in the several fishes provided with electric organs
that these are situated in different parts of the body,—that
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
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
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
difficulty disappears,
leaving only the lesser yet still great difficulty; namely, by what graduated steps these organs have arisen and
been developed in each separate fish. |
| 1 blocks not present in 1859 1860 1861; present in 1866 1869 1872 | | The luminous organs which occur only
in a few insects, belonging to widely different families
and orders, and
which are situated in different parts of the body,
offer
a
difficulty almost exactly parallel with that of the electric organs.
|
| In all these cases of two very distinct species furnished with apparently 1859 1860 1861 |
| Other cases could be given; for instance in plants, the very curious contrivance of a mass of pollen-grains, borne on a foot-stalk with an adhesive gland, is apparently 1866 1869 |
| Other similar cases could be given; for instance in plants, the very curious contrivance of a mass of pollen-grains, borne on a foot-stalk with an adhesive gland, is apparently 1872 |
| anomalous organ, it should be observed that, although the general appearance and function of the organ may be the same, yet some fundamental difference can generally be detected. 1859 1860 1861 |
| in Orchis and Asclepias,—genera almost as remote as is possible amongst flowering plants. 1866 1869 |
| in Orchis and Asclepias,— genera almost as remote as is possible amongst flowering plants; but here again the parts are not homologous. 1872 |
| I am inclined to believe that in nearly the same way as two men have sometimes independently hit on the very same invention, so natural selection, working for the good of each being and taking advantage of analogous variations, has sometimes modified in very nearly 1859 1860 1861 |
| In all these cases of two species, far removed from each other in the scale of organisation, being furnished with a similar anomalous organ, it should be observed that although the general appearance and function of the organ may be 1866 |
| In all such cases of two species, far removed from each other in the scale of organisation, being furnished with similar anomalous organs, it should be observed that although the general appearance and function of the organ may be 1869 |
| In all cases of beings, far removed from each other in the scale of organisation, which are furnished with similar and peculiar organs, it will be found that although the general appearance and function of the organs may be 1872 |
| the 1859 1860 1861 1872 | | identically the 1866 1869 |
| same 1859 1860 1861 | | same, 1866 1869 1872 |
| manner two parts in two organic beings, which beings owe but little of their structure in common to inheritance from the same ancestor. 1860 1861 |
| manner two parts in two organic beings, which owe but little of their structure in common to inheritance from the same ancestor. 1859 |
| yet some fundamental difference between them can always, or almost always, be detected. 1866 1869 |
| yet fundamental differences between them can always be detected. 1872 |
|
