[] The Eyes of Spiders, (in some four, in some six, and in some eight) are placed all in the fore-front of their Head, (which is round, and without any Neck) all diaphanous and transparent, like a Locket of Diamonds, &c. neither wonder why Providence should be so anomalous in this Animal, more than in any other we know of. For, 1. Since they wanting a Neck, cannot move their Head, it is requisite that Defect should be supplied by the multiplicity of Eyes. 2. Since they were to live by catching so nimble a Prey as a Fly is, they ought to see her every way, and to take her per saltum, (as they do) without any Motion of the Head to discover her: Which Motion would have scared away so timorous an Insect. Power’s Micros. Observ. pag. 11.
The Eyes of the Cameleon resemble a Lens, or Convex Glass, set in a versatile globular Socket, which she turneth backward, or any way, without moving her Head; and ordinarily the one a contrary, or quite different way from the other. Dr. Goddard in Phil. Tran. Nᵒ. 137.
But what is more extraordinary in this Motion [of the Cameleon’s Eye] is to see one of the Eyes move, whilst the other remains immoveable; and the one to turn forward, at the same time that the other looketh behind; the one to look up to the Sky, when the other is fixed on the Ground. And these Motions to be so extreme, that they do carry the Pupilla under the Crest which makes the Eye-brow, and so far into the Canthi, or Corners of the Eyes, that the Sight can discern whatever is done just behind it, and directly before, without turning the Head, which is fastned to the Shoulders. Mem. for a Nat. Hist. in Anatom. Dissect. at Paris. Diss. of Camel. pag. 22.
[k] Snails send out their Eyes at a distance, they being contained in their four Horns, like atramentous Spots, fitted to the end of their Horns, or rather to the ends of those black Filaments or optick Nerves, which are sheathed in her Horns, as Dr. Power wordeth it. Obs. 31. pag. 36. So the ingenious Dr. Lister. Exercit. Anat. Cochl. & Limac.
[l] Vid. [l. 8. c. 3. Note (a).]
[m] Severinus is of Aristotle’s, Pliny’s, and Alb. Magnus’s Opinion, that the Mole hath no Sight; G. Seger denies any Humour to be therein, but thinks they may probably see, because Nature made nothing in vain. But Borrichius saith, their Eyes have appendiculam nerveam in cerebrum euntem, cujus beneficio globuli illi [the little Eyes] extra pellem facilè poterant exseri, retrahique pro arbitrio——In illis oculorum globulis humor aqueus copiose satis natabat; cæterorum non nisi tenue vestigiem. Blas. Anat. Anim. c. 35.
Et quoniam Natura hoc vitæ genus ipsi destinavit, etiam perquàm exiguos Oculos——dedit eo concilio, ut ii, pretiosissima corporis pars, à terræ pulvere nè affligerentur. Ii insuper pilis recti, &c. Humores illis oculis insunt, & tunica nigra, uvea, se prodit. Ad hos tramite alio nervus venit. Schneider in Blas. ibid.
Some time since I made divers accurate Dissections of the Eyes of Moles, with the help of Microscopes, having a doubt whether what we take to be Eyes, were such or no. And upon a strict Scrutiny I plainly could distinguish the Vitreous and Crystalline Humours, yea, the Ligamentum Ciliare, and the atramentaceous Mucus. The Pupil I could manifestly discern to be round, and the Cornea copped, or conical: The Eye is at a great distance from the Brain, the Optick Nerve very slender and long, reaching from the Eye through the intermediate Flesh, and so passeth to the Brain, along with the pair of Nerves reaching to the Nose, which are much the largest that are in all the Animal. These Creatures, I imagine, have the Faculty of withdrawing their Eyes, if not quite into the Head, (as Snails) yet more or less within the Hair, as they have more or less Occasion to use or guard their Eyes.
Galen saith, Moles have Eyes, the Crystalline and Vitreous Humours, encompassed with Tunicks. De Us. Part. l. 14. c. 6. So accurate an Anatomist was he for his Time.
[n] Pliny tells us of a sort of Heron with but one Eye, but ’twas only by hear-say. Inter Aves Ardeolarum genere, quos Leucos vocant, altero oculo carere tradunt. Nat. Hist. l. 11. c. 37. So the King of the Nigræ that hath but one Eye, and that in his Forehead, l. 6. c. 30. Which Fables I take notice of more for the Reader’s Diversion, than any Truth in them.