Part 28

Whil’st I was examining and considering the curious _Mechanism_ of the wings, I observ’d that under the wings of most kind of Flies, Bees, &c. there were plac’d certain _pendulums_ or extended drops (as I may so call them from their resembling motion and figure) for they much resembled a long hanging drop of some transparent viscous liquor; and I observed them constantly to move just before the wings of the Fly began to move, so that at the first sight I could not but ghess, that there was some excellent use, as to the regulation of the motion of the wing, and did phancy, that it might be something like the handle of a Cock, which by vibrating to and fro, might, as ’twere, open and shut the Cock, and thereby give a passage to the determinate influences into the Muscles; afterwards, upon some other trials, I suppos’d that they might be for some use in respiration, which for many reasons I suppose those Animals to use, and, me thought, it was not very improbable, but that they might have convenient passages under the wings for the emitting, at least, of the air, if not admitting, as in the gills of Fishes is most evident; or, perhaps, this _Pendulum_ might be somewhat like the staff to a Pump, whereby these creatures might exercise their _Analogous_ lungs, and not only draw in, but force out, the air they live by: but these were but conjectures, and upon further examination seem’d less probable.

The fabrick of the wing, as it appears through a moderately magnifying _Microscope_, seems to be a body consisting of two parts, as is visible in the 4. _Figure_ of the 23. _Scheme_; and by the 2. _Figure_ of the 26. _Scheme_; the one is a quilly or finny substance, consisting of several long, slender and variously bended quills or wires, something resembling the veins of leaves; these are, as ’twere, the finns or quills which stiffen the whole _Area_, and keep the other part distended, which is a very thin transparent skin or membrane variously folded, and platted, but not very regularly, and is besides exceeding thickly bestuck with innumerable small bristles, which are onely perceptible by the bigger magnifying _Microscope_, and not with that neither, but with a very convenient augmentation of sky-light projected on the Object with a burning Glass, as I have elsewhere shew’d, or by looking through it against the light.

In steed of these small hairs, in several other Flies, there are infinite of small Feathers, which cover both the under and upper sides of this thin film as in almost all the sorts of Butterflies and Moths: and those small parts are not onely shap’d very much like the feathers of Birds, but like those variegated with all the variety of curious bright and vivid colours imaginable; and those feathers are likewise so admirably and delicately rang’d, as to compose very fine flourishings and ornamental paintings, like _Turkie_ and _Persian_ Carpets, but of far more surpassing beauty, as is evident enough to the naked eye, in the painted wings of Butterflies, but much more through an ordinary _Microscope_.

Intermingled likewise with these hairs, may be perceived multitudes of little pits, or black spots, in the extended membrane, which seem to be the root of the hairs that grow on the other side; these two bodies seem dispers’d over the whole surface of the wing.

The hairs are best perceiv’d, by looking through it against the light, or, by laying the wing upon a very white piece of Paper, in a convenient light, for thereby every little hair most manifestly appears; a _Specimen_ of which you may observe drawn in the fourth _Figure_ of the 23. _Scheme_, AB, CD, EF whereof represent some parts of the bones or quills of the wing, each of which you may perceive to be cover’d over with a multitude of scales, or bristles, the former AB, is the biggest stem of all the wing, and may be properly enough call’d the cut-air, it being that which terminates and stiffens the formost edge of the wing; the fore-edge of this is arm’d with a multitude of little brisles, or Tenter-hooks, in some standing regular and in order, in others not; all the points of which are directed from the body towards the tip of the wing, nor is this edge onely thus fring’d, but even all the whole edge of the wing is covered with a small fringe, consisting of short and more slender brisles.

This Subject, had I time, would afford excellent matter for the contemplation of the nature of wings and of flying, but, because I may, perhaps, get a more convenient time to prosecute that speculation, and recollect several Observations that I have made of that particular. I shall at present proceed to

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Observ. XXXIX. _Of the Eyes and Head of a _Grey drone-Fly_, and of several other creatures._

I took a large grey _Drone-Fly_, that had a large head, but a small and slender body in proportion to it, and cutting off its head, I fix’d it with the forepart or face upwards upon my Object Plate (this I made choice of rather then the head of a great blue Fly, because my enquiry being now about the eyes, I found this Fly to have, first the biggest clusters of eyes in proportion to his head, of any small kind of Fly that I have yet seen, it being somewhat inclining towards the make of the large _Dragon-Flies_. Next, because there is a greater variety in the knobs or balls of each cluster, then is of any small Fly.) Then examining it according to my usual manner, by varying the degrees of light, and altering its position to each kinde of light, I drew that representation of it which is delineated in the 24. _Scheme_, and found these things to be as plain and evident, as notable and pleasant.

_First_, that the greatest part of the face, nay, of the head, was nothing else but two large and _protuberant_ bunches, or _prominent_ parts, ABCDEA, the surface of each of which was all cover’d over, or shap’d into a multitude of small _Hemispheres_, plac’d in a _triagonal_ order, that being the closest and most compacted, and in that order, rang’d over the whole surface of the eye in very lovely rows, between each of which, as is necessary, were left long and regular trenches, the bottoms of every of which, were perfectly intire and not at all perforated or drill’d through, which I most certainly was assured of, by the regularly reflected Image of certain Objects which I mov’d to and fro between the head and the light. And by examining the _Cornea_ or outward skin, after I had stript it off from the several substances that lay within it, and by looking both upon the inside and against the light.

_Next_, that of those multitudes of _Hemispheres_, there were observable two degrees of bigness, the half of them that were lowermost, and look’d toward the ground or their own leggs, namely, CDE, CDE being a pretty deal smaller then the other, namely, ABCE, ABCE, that look’d upward, and side-ways, or foreright, and backward, which variety I have not found in any other small Fly.

_Thirdly_, that every one of these _Hemispheres_, as they seem’d to be pretty neer the true shape of a _Hemisphere_, so was the surface exceeding smooth and regular, reflecting as exact, regular, and perfect an Image of any Object from the surface of them, as a small Ball of Quick-silver of that bigness would do, but nothing neer so vivid, the reflection from these being very languid, much like the reflection from the outside of Water, Glass, Crystal, &c. In so much that in each of these _Hemispheres_, I have been able to discover a Land-scape of those things which lay before my window, one thing of which was a large Tree, whose trunk and top I could plainly discover, as I could also the parts of my window, and my hand and fingers, if I held it between the Window and the Object; a small draught of nineteen of which, as they appear’d in the bigger Magnifying-glass to reflect the Image of the two windows of my Chamber, are delineated in the third _Figure_ of the 23. _Scheme_.

_Fourthly_, that these rows were so dispos’d, that there was no quarter visible from his head that there was not some of these _Hemispheres_ directed against, so that a Fly may be truly said to have _an eye every way_, and to be really _circumspect_. And it was further observable, that that way where the trunk of his body did hinder his prospect backward, these _protuberances_ were elevated, as it were, above the plain of his shoulders and back, so that he was able to see backwards also over his back.

_Fifthly_, in living Flies, I have observ’d, that when any small mote or dust, which flies up and down the air, chances to light upon any part of these knobs, as it is sure to stick firmly to it and not fall, though through the _Microscope_ it appears like a large stone or stick (which one would admire, especially since it is no ways probable that there is any wet or glutinous matter upon these _Hemispheres_, but I hope I shall render the reason in another place) so the Fly presently makes use of his two fore-feet in stead of eye-lids, with which, as with two Brooms or Brushes, they being all bestuck with Brisles, he often sweeps or brushes off what ever hinders the prospect of any of his _Hemispheres_, and then, to free his leggs from that dirt, he rubs them one against another, the pointed Brisles or Tenters of which looking both one way, the rubbing of them to and fro one against another, does cleanse them in the same manner as I have observ’d those that Card Wool, to cleanse their Cards, by placing their Cards, so as the teeth of both look the same way, and then rubbing them one against another. In the very same manner do they brush and cleanse their bodies and wings, as I shall by and by shew; other creatures have other contrivances for the cleansing and cleering their eyes.

_Sixthly_ that the number of the _Pearls_ or _Hemispheres_ in the clusters of this Fly, was neer 14000. which I judged by numbering certain rows of them several ways, and casting up the whole content, accounting each cluster to contain about seven thousand Pearls, three thousand of which were of a size, and consequently the rows not so thick, and the foure thousand I accounted to be the number of the smaller Pearls next the feet and _proboscis_. Other Animals I observ’d to have yet a greater number, as the _Dragon-Fly_ or _Adderbolt_: And others to have a much less company, as an _Ant_, &c. and several other small Flies and Insects.

_Seventhly_, that the order of these eies or _Hemispheres_ was altogether curious and admirable, they being plac’d in all kind of Flies, and _aerial_ animals, in a most curious and regular ordination of triangular rows, in which order they are rang’d the neerest together that possibly they can, and consequently leave the least pits or trenches between them. But in _Shrimps_, _Crawfishes_, _Lobsters_, and such kinds of _Crustaceous_ water Animals, I have yet observ’d them rang’d in a quadrangular order, the rows cutting each other at right angles, which as it admits of a less number of Pearls in equal surfaces; so have those creatures a recompence made them, by having their eyes a little movable in their heads, which the other altogether want. So infinitely wise and provident do we find all the Dispensations in Nature, that certainly _Epicurus_, and his followers, must very little have consider’d them, who ascrib’d those things to the production of chance, that wil, to a more attentive considerer, appear the products of the highest Wisdom and Providence.

Upon the Anatomy or Dissection of the Head, I observ’d these particulars:

First, that this outward skin, like the _Cornea_ of the eyes of the greater Animals, was both flexible and transparent, and seem’d, through the _Microscope_ perfectly to resemble the very substance of the _Cornea_ of a man’s eye; for having cut out the cluster, and remov’d the dark and _mucous_ stuff that is subjacent to it, I could see it transparent like a thin piece of skin, having as many cavities in the inside of it, and rang’d in the same order as it had _protuberances_ on the outside, and this propriety, I found the same in all the Animals that had it, whether Flies or Shell-Fish.

Secondly, I found that all Animals that I have observ’d with those kind of eyes; have within this _Cornea_, a certain cleer liquor or juice, though in a very little quantity, and,

I observ’d thirdly, that within that cleer liquor, they had a kind of dark _mucous_ lining, which was all spread round within the cavity of the clutter, and seem’d very neer adjoining to it, the colour of which, in some Flies, was grey; in others, black, in others red; in others, of a mix’d colour; in others, spotted; and that the whole clusters, when look’d on whilst the Animal was living, or but newly kill’d, appear’d of the same colour that this coat (as I may so call it) appear’d of, when that outward skin, or _Cornea_, was remov’d.

Fourthly, that the rest of the capacity of the clusters was in some, as in Dragon Flies, &c. hollow, or empty; in others fill’d with some kind of substance; in blue Flies, with a reddish musculous substance, with _fibres_ tending from the center or bottom outwards; and divers other, with various and differing kinds of substances.

That this curious contrivance is the organ of sight to all those various _Crustaceous_ Animals, which are furnish’d with it, I think we need not doubt, if we consider but the several congruities it has with the eyes of greater creatures.

As first, that it is furnish’d with a _Cornea_, with a _transparent humour_, and with a _uvea_ or _retina_, that the Figure of each of the small _Hemispheres_ are very _Spherical_, exactly polish’d, and most vivid, lively and plump, when the Animal is living, as in greater Animals, and in like manner dull, flaccid, and irregular, or shrunk, when the Animal is dead.

Next, that those creatures that are furnish’d with it, have no other organs that have any resemblance to the known eyes of other creatures.

Thirdly, that those which they call the eyes of Crabs, Lobsters, Shrimps, and the like, and are really so, are _Hemispher’d_, almost in the same manner as these of Flies are. And that they really are so, I have very often try’d, by cutting off these little movable knobs, and putting the creature again into the water, that it would swim to and fro, and move up and down as well as before, but would often hit it self against the rocks or stones; and though I put my hand just before its head, it would not at all start or fly back till I touch’d it, whereas whil’st those were remaining, it would start back, and avoid my hand or a stick at a good distance before it touch’d it. And if in _crustaceous_ Sea-animals, then it seems very probable also, that these knobs are the eyes in _crustaceous_ Insects, which are also of the same kind, onely in a higher and more active Element; this the conformity or congruity of many other parts common to either of them, will strongly argue, their _crustaceous_ armour, their number of leggs, which are six, beside the two great claws, which answer to the wings in Insects; and in all kind of Spiders, as also in many other Insects that want wings, we shall find the compleat number of them, and not onely the number, but the very shape, figure, joints, and claws of Lobsters and Crabs, as is evident in Scorpions and Spiders, as is visible in the second _Figure_ of the 31. _Scheme_, and in the little Mite-worm, which I call a Land-crab, describ’d in the second Figure of the 33. _Scheme_, but in their manner of generation being oviparous, &c. And it were very worthy observation, whether there be not some kinds of transformation and metamorphosis in the several states of _crustaceous_ water-animals, as there is in several sorts of Insects; for if such could be met with, the progress of the variations would be much more conspicuous in those larger Animals, then they can be in any kind of Insects our colder Climate affords.

These being their eyes, it affords us a very pretty Speculation to contemplate their manner of vision, which, as it is very differing from that of _biocular_ Animals, so is it not less admirable.

That each of these Pearls or _Hemispheres_ is a perfect eye, I think we need not doubt, if we consider onely the outside or figure of any one of them, for they being each of them cover’d with a transparent protuberant _Cornea_, and containing a liquor within them, resembling the watry or glassie humours of the eye, must necessarily refract all the parallel Rays that fall on them out of the air, into a point not farr distant within them, where (in all probability) the _Retina_ of the eye is placed, and that opacous, dark, and mucous inward coat that (I formerly shew’d) I found to subtend the concave part of the cluster is very likely to be that _tunicle_ or coat, it appearing through the _Microscope_ to be plac’d a little more than a Diameter of those Pearls below or within the _tunica cornea_. And if so, then is there in all probability, a little Picture or Image of the objects without, painted or made at the bottom of the _Retina_ against every one of those Pearls, so that there are as many impressions on the _Retina_ or opacous skin, as there are Pearls or _Hemispheres_ on the cluster. But because it is impossible for any protuberant surface whatsoever, whether _sphærial_ or other, so to refract the Rays that come from farr remote _lateral_ points of any Object as to collect them again, and unite them each in a distinct point, and that onely those Rays which come from some point that lies in the _Axis_ of the Figure produc’d, are so accurately refracted to one and the same point again, and that the _lateral_ Rays, the further they are remov’d, the more imperfect is their refracted confluence; It follows therefore, that onely the Picture of those parts of the external objects that lie in, or neer, the _Axis_ of each _Hemisphere_, are discernably painted or made on the _Retina_ of each _Hemisphere_, and that therefore each of them can distinctly sensate or see onely those parts which are very neer perpendicularly oppos’d to it, or lie in or neer its optick _Axis_. Now, though there may be by each of these eye-pearls, a representation to the Animal of a whole _Hemisphere_ in the same manner as in a man’s eye there is a picture or sensation in the _Retina_ of all the objects lying almost in an _Hemisphere_; yet, as in a man’s eye also, there are but some very few points which liyng in, or neer, the optick _Axis_ are distinctly discern’d: So there may be multitudes of Pictures made of an Object in the several Pearls, and yet but one, or some very few that are distinct; The representation of any object that is made in any other Pearl, but that which is directly, or very neer directly, oppos’d, being altogether confus’d and unable to produce a distinct vision.

So that we see, that though it has pleas’d the All-wise Creator, to indue this creature with such multitudes of eyes, yet has he not indued it with the faculty of seeing more then another creature; for whereas this cannot move his head, at least can move it very little, without moving his whole body, _biocular_ creatures can in an instant (or _the twinkling of an eye_, which, being very quick, is vulgarly used in the same signification) move their eyes so as to direct the optick _Axis_ to any point; nor is it probable, that they are able to see attentively at one time more then one Physical point; for though there be a distinct Image made in every eye, yet ’tis very likely, that the observing faculty is only imploy’d about some one object for which they have most concern.

Now, as we accurately distinguish the site or position of an Object by the motion of the Muscles of the eye requisite to put the optick Line in a direct position, and confusedly by the position of the imperfect Picture of the object at the bottom of the eye; so are these _crustaceous_ creatures able to judge confusedly of the position of objects by the Picture or impression made at the bottom of the opposite Pearl, and distinctly by the removal of the attentive or observing faculty, from one Pearl to another, but what this faculty is, as it requires another place, so a much deeper speculation. Now, because it were impossible, even with this multitude of eye-balls, to see any object distinct (for as I hinted before, onely those parts that lay in, or very neer, the optick Lines could be so) the Infinitely wise Creator has not left the creature without a power of moving the head a little in _Aerial crustaceous_ animals, and the very eyes also in _crustaceous_ Sea-animals; so that by these means they are inabled to direct some optick line or other against any object, and by that means they have the visive faculty as compleat as any Animal that can move its eyes.

Distances of Objects also, ’tis very likely they distinguish, partly by the consonant impressions made in some two convenient Pearls, one in each cluster; for, according as those congruous impressions affect, two Pearls neerer approach’d to each other, the neerer is the Object, and the farther they are distant, the more distant is the Object: partly also by the alteration of each Pearl, requisite to make the Sensation or Picture perfect; for ’tis impossible that the Pictures of two Objects, variously distant, can be perfectly painted, or made on the same _Retina_ or bottom of the eye not altered, as will be very evident to any one that shall attentively consider the nature of refraction. Now, whether this alteration may be in the Figure of the _Cornea_, in the motion of access or recess of the _Retina_ towards the _Cornea_, or in the alteration of a crystalline humour, if such there be, I pretend not to determine; though I think we need not doubt, but that there may be as much curiosity of contrivance and structure in every one of these Pearls, as in the eye of a Whale or Elephant, and the almighty’s _Fiat_ could as easily cause the existence of the one as the other; and as one day and a thousand years are the same with him, so may one eye and ten thousand.

This we may be sure of, that the filaments or sensative parts of the _Retina_ must be most exceedingly curious and minute, since the whole Picture it self is such; what must needs the component parts be of that _Retina_, which distinguishes the part of an object’s Picture that must be many millions of millions less then that in a man’s eye? And how exceeding curious and subtile must the component parts of the _medium_ that conveys light be, when we find the instrument made for its reception or refraction to be so exceedingly small? we may, I think, from this speculation be sufficiently discouraged from hoping to discover by any optick or other instrument the determinate bulk of the parts of the _medium_ that conveys the pulse of light, since we find that there is not less accurateness shewn in the Figure and polish of those exceedingly minute lenticular surfaces, then in those more large and conspicuous surfaces of our own eyes. And yet can I not doubt, but that there is a determinate bulk of those parts, since I find them unable to enter between the parts of Mercury, which being in motion, must necessarily have pores, as I shall elsewhere shew, and here pass by, as being a digression.

As concerning the horns FF, the feelers or smellers, GG, the _Proboscis_ HH, and I, the hairs and brisles, KK, I shall indeavour to describe in the 42. _Observation_.

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Observ. XL. _Of the Teeth of a _Snail_._