The luminous organs which occur
only
in a few insects, belonging to widely different
families | families 1866 1869 | | families, 1872 |
| orders, but 1866 | | orders, and 1869 | orders, but 1872 |
| their bodies, 1866 | | the body, 1869 1872 |
| offer 1866 1869 | | offer, 1872 |
| a 1866 1869 |
| under our present state of ignorance, a 1872 |
| 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 |
| In all these cases of two very distinct species furnished with apparently 1859 1860 1861 |
| 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 |
| in Orchis and Asclepias,—genera almost as remote as is possible amongst flowering plants. 1866 1869 |
| 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; but here again the parts are not homologous. 1872 |
| 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 |
| 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 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 |
| identically the 1866 1869 | | the 1859 1860 1861 1872 |
| same, 1866 1869 1872 | | same 1859 1860 1861 |
| yet some fundamental difference between them can always, or almost always, be detected. 1866 1869 |
| manner two parts in two organic beings, which owe but little of their structure in common to inheritance from the same ancestor. 1859 |
| 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 |
| yet fundamental differences between them can always be detected. 1872 |
| 10 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | | For instance, the eyes of cephalopods or cuttle-fish and of vertebrate animals appear wonderfully alike; and in such widely sundered groups no part of this resemblance can be due to inheritance from a common progenitor.
Mr. Mivart has advanced this case as one of special difficulty, but I am unable to see the force of his argument.
An organ for vision must be formed of transparent tissue, and must include some sort of lens for throwing an image at the back of a darkened chamber.
Beyond this superficial resemblance, there is hardly any real similarity between the eyes of cuttle-fish and vertebrates, as may be seen by consulting Hensen's admirable memoir on these organs in the Cephalopoda.
It is impossible for me here to enter on details, but I may specify a few of the points of difference.
The crystalline lens in the higher cuttle-fish consists of two parts, placed one behind the other like two lenses, both having a very different structure and disposition to what occurs in the vertebrata.
The retina is wholly different, with an actual inversion of the elemental parts, and with a large nervous ganglion included within the membranes of the eye.
The relations of the muscles are as different as it is possible to conceive, and so in other points.
Hence it is not a little difficult to decide how far even the same terms ought to be employed in describing the eyes of the Cephalopoda and Vertebrata.
It is, of course, open to any one to deny that the eye in either case could have been developed through the natural selection of successive, slight variations; but if this be admitted in the one case, it is clearly possible in the other; and fundamental differences of structure in the visual organs of two groups might have been anticipated, in accordance with this view of their manner of formation.
|
| I am inclined to believe that, in 1866 1869 |
| As two men have sometimes independently hit on 1872 |
| manner as two men have sometimes independently hit on the same 1866 1869 |
| OMIT 1872 |
| natural 1866 1869 |
| in the several foregoing cases it appears that natural 1872 |
| being 1866 1869 | | being, 1872 |
| analogous 1866 1869 | | all favourable 1872 |
| sometimes modified in nearly the same way two organs in two 1866 1869 |
| produced similar organs, as far as function is concerned, in distinct 1872 |
| organic 1866 1872 | | distinct organic 1869 |
| but little 1866 1869 | | none 1872 |
|
Fritz Müller, in
a remarkable work recently published, has discussed a case nearly parallel with that of electric fishes, luminous insects, &c.; he undertook the laborious examination of this case in | a remarkable work recently published, has discussed a case nearly parallel with that of electric fishes, luminous insects, &c.; he undertook the laborious examination of this case in 1866 |
| a remarkable work recently published, has investigated a nearly parallel case, in 1869 |
| OMIT 1872 |
| views advanced by me 1866 |
| views advanced 1869 |
| conclusions arrived at 1872 |
| volume. 1866 1869 |
| volume, has followed out with much care a nearly similar line of argument. 1872 |
| members which are 1866 |
| species which possess an air-breathing apparatus, and are 1869 |
| species, possessing an air-breathing apparatus and 1872 |
| water 1866 | | water. 1869 1872 |
| possess 1866 | possess 1869 1872 |
| air-breathing 1866 | air-breathing 1869 1872 |
| apparatus. 1866 | apparatus. 1869 1872 |
| characters: 1866 | | characters; 1869 1872 |
| the structure of 1866 |
| OMIT 1869 1872 |
|
