Sclerotic, retina, choroid, vitreous humour, lens, aqueous humour, all are present.

The correspondence is wonderfully complete, and there can hardly be any hesitation in saying that for such an exact, prolonged, and correlated series of similar structures to have been brought about in two independent instances by merely indefinite and minute accidental variations, is an improbability which amounts practically to impossibility.

Moreover, we have here again the same imperfection of the four-gilled cephalopod, as compared with the two-gilled, and therefore (if the latter proceeded from the former) a similar indication of a certain comparative rapidity of development.
Finally, and this is perhaps one of the most curious circumstances, the process of formation appears to have been, at least in some respects, the same in the eyes of these molluscous animals as in the eyes of vertebrates.
For in these latter the cornea is at first perforated, while different degrees of perforation of the same part are presented by different adult cuttle-fishes--large in the calamaries, smaller in the octopods, and reduced to a minute foramen in the true cuttle-fish sepia.
Some may be disposed to object that the conditions requisite for effecting vision are so rigid that similar results in all cases must be independently arrived at.

But to this objection it may well be replied that Nature herself has demonstrated that there is no such necessity as to the details of the process.

For in the higher Annulosa, such as the dragon-fly, we meet with an eye of an unquestionably very high degree of efficiency, but formed on a type of structure only remotely comparable with that of the fish or the cephalopod.