Micrographia Part 17

Observ. x.x.xVI. _Of _Peac.o.ks_, _Ducks_, and other _Feathers_ of changeable colours._

The parts of the Feathers of this glorious Bird appear, through the _Microscope_, no less gaudy then do the whole Feathers; for, as to the naked eye 'tis evident that the stem or quill of each Feather in the tail sends out mult.i.tudes of _Lateral_ branches, such as AB in the third Figure of the 22. _Scheme_ represents a small part of about 1/32 part of an Inch long, and each of the _lateral_ branches emit mult.i.tudes of little sprigs, threads or hairs on either side of them, such as CD, CD, CD, so each of those threads in the _Microscope_ appears a large long body, consisting of a mult.i.tude of bright reflecting parts, whose Figure 'tis no easie matter to determine, as he that examines it shall find; for every new position of it to the light makes it perfectly seem of another form and shape, and nothing what it appear'd a little before; nay, it appear'd very differing ofttimes from so seemingly inconsiderable a circ.u.mstance, that the interposing of ones hand between the light and it, makes a very great change, and the opening or shutting a Cas.e.m.e.nt and the like, very much diversifies the appearance. And though, by examining the form of it very many ways, which would be tedious here to enumerate, I suppose I have discover'd the true Figure of it, yet oftentimes, upon looking on it in another posture, I have almost thought my former observations deficient, though indeed, upon further examination, I have found even those also to confirm them.

These threads therefore I find to be a _congeries_ of small _Laminae_ or plates, as eeeee, &c. each of them shap'd much like this of abcd, in the fourth _Figure_, the part ac being a ridge, prominency, or stem, and b and d the corners of two small thin Plates that grow unto the small stalk in the middle, so that they make a kind of little feather; each of these Plates lie one close to another, almost like a company of sloping ridge or gutter Tyles; they grow on each side of the stalk opposite to one another, by two and two, from top to bottom, in the manner express'd in the fifth Figure, the tops of the lower covering the roots of the next above them; the under side of each of these laminated bodies, is of a very dark and opacous substance, and suffers very few Rays to be trajected, but reflects them all toward that side from whence they come, much like the foil of a Looking-gla.s.s; but their upper sides seem to me to consist of a mult.i.tude of thin plated bodies, which are exceeding thin, and lie very close together, and thereby, like mother of Pearl sh.e.l.ls, do not onely reflect a very brisk light, but tinge that light in a most curious manner; and by means of various positions, in respect of the light, they reflect back now one colour, and then another, and those most vividly.

Now, that these colours are onely _fantastical_ ones, that is, such as arise immediately from the refractions of the light, I found by this, that water wetting these colour'd parts, destroy'd their colours, which seem'd to proceed from the alteration of the reflection and refraction. Now, though I was not able to see those hairs at all transparent by a common light, yet by looking on them against the Sun, I found them to be ting'd with a darkish red colour, nothing a-kin to the curious and lovely greens and blues they exhibited.

What the reason of colour seems to be in such thin plated bodies, I have elsewhere shewn. But how water cast upon those threads destroys their colours, I suppose to be perform'd thus; The water falling upon these plated bodies from its having a greater congruity to Feathers then the Air, insinuates it self between those Plates, and so extrudes the strong reflecting Air, whence both these parts grow more transparent, as the _Microscope_ informs, and colourless also, at best retaining a very faint and dull colour. But this wet being wasted away by the continual evaporations and steams that pa.s.s through them from the Peac.o.c.k, whil'st that Bird is yet alive, the colours again appear in their former l.u.s.ter, the _interst.i.tia_ of these Plates being fill'd with the strongly reflecting Air.

The beauteous and vivid colours of the Feathers of this Bird, being found to proceed from the curious and exceeding smalness and fineness of the reflecting parts, we have here the reason given us of all those gauderies in the apparel of other Birds also, and how they come to exceed the colours of all other kinds of Animals, besides Insects; for since (as we here, and elsewhere also shew) the vividness of a colour, depends upon the fineness and transparency of the reflecting and refracting parts; and since our _Microscope_ discovers to us, that the component parts of feathers are such, and that the hairs of Animals are otherwise; and since we find also by the Experiment of that n.o.ble and most Excellent Person I formerly named; that the difference between Silk and Flax, as to its colour, is nothing else (for Flax reduc'd to a very great fineness of parts, both white and colour'd, appears as white and as vivid as any Silk, but loses that brightness and its Silken aspect as soon as it is twisted into thread, by reason that the component parts, though very small and fine, are yet pliable flakes, and not cylinders, and thence, by twisting, become united into one opacous body, whereas the threads of Silk and Feathers retain their l.u.s.tre, by preserving their cylindrical form intire without mixing; so that each reflected and refracted beam that composes the gloss of Silk, preserves its own property of modulating the light intire); And since we find the same confirm'd by many other Experiments elsewhere mentioned, I think we may safely conclude this for an Axiome, that wheresoever we meet with transparent bodies, spun out into very fine parts, either cleer, or any ways ting'd, the colours resulting from such a _composition_ must necessarily be very glorious, vivid, and cleer, like those of Silk and Feathers. This may perhaps hint some usefull way of making other bodies, besides Silk, be susceptible of bright tinctures, but of this onely by the by.

The changeable colour'd Feathers also of Ducks, and several other Birds, I have found by examination with my _Microscope_, to proceed from much the same causes and textures.

Observ. x.x.xVII. _Of the Feet of _Flies_, and several other _Insects_._

The foot of a Fly (delineated in the first _Figure_ of the 23. _Scheme_, which represents three joints, the two Tallons, and the two Pattens in a flat posture; and in the second _Figure_ of the same _Scheme_, which represents onely one joint, the Tallons and Pattens in another posture) is of a most admirable and curious contrivance, for by this the Flies are inabled to walk against the sides of Gla.s.s, perpendicularly upwards, and to contain themselves in that posture as long as they please; nay, to walk and suspend themselves against the under surface of many bodies, as the ceiling of a room, or the like, and this with as great a seeming facility and firmness, as if they were a kind of _Antipodes_, and had a _tendency_ upwards, as we are sure they have the contrary, which they also evidently discover, in that they cannot make themselves so light, as to stick or suspend themselves on the under surface of a Gla.s.s well polish'd and cleans'd; their suspension therefore is wholly to be ascrib'd to some Mechanical contrivance in their feet; which, what it is, we shall in brief explain, by shewing, that its Mechanism consists princ.i.p.ally in two parts, that is, first its two Claws, or Tallons, and secondly, two Palms, Pattens, or Soles.

The two Tallons are very large, in proportion to the foot, and handsomly shap'd in the manner describ'd in the _Figures_, by AB, and AC, the bigger part of them from A to _dd_, is all hairy, or brisled, but toward the top, at C and B smooth, the tops or points, which seem very sharp turning downwards and inwards, are each of them mov'd on a joint at A, by which the Fly is able to open or shut them at pleasure, so that the points B and C being entered in any pores, and the Fly endeavouring to shut them, the Claws not onely draw one against another, and so fasten each other, but they draw the whole foot, GGADD forward, so that on a soft footing, the tenters or points GGGG, (whereof a Fly has about ten in each foot, to wit, two in every joint) run into the pores, if they find any, or at least make their way; and this is sensible to the naked eye, in the feet of a _Chafer_, which, if he be suffer'd to creep over the hand, or any other part of the skin of ones body, does make his steps as sensible to the touch as the sight.

But this contrivance, as it often fails the _Chafer_, when he walks on hard and close bodies, so would it also our Fly, though he be a much lesser, and nimbler creature, and therefore Nature has furnish'd his foot with another _additament_ much more curious and admirable, and that is, with a couple of Palms, Pattens or Soles DD, the structure of which is this:

From the bottom or under part of the last joint of his foot, K, arise two small thin plated h.o.r.n.y substances, each consisting of two flat pieces, DD, which seem to be flexible, like the covers of a Book, about FF, by which means, the plains of the two sides EE, do not always lie in the same plain, but may be sometimes shut closer, and so each of them may take a little hold themselves on a body; but that is not all, for the under sides of these Soles are all beset with small brisles, or tenters, like the Wire teeth of a Card used for working Wool, the points of all which tend forwards, hence the two Tallons drawing the feet forwards, as I before hinted, and these being applied to the surface of the body with all the points looking the contrary way, that is, forwards and outwards, if there be any irregularity or yielding in the surface of the body, the Fly suspends it self very firmly and easily, without the access or need of any such Sponges fill'd with an imaginary _gluten_, as many have, for want of good Gla.s.ses, perhaps, or a troublesome and diligent examination, suppos'd.

Now, that the Fly is able to walk on Gla.s.s, proceeds partly from some ruggedness of the surface: and chiefly from a kind of tarnish, or dirty smoaky substance, which adheres to the surface of that very hard body; and though the pointed parts cannot penetrate the substance of Gla.s.s, yet may they find pores enough in the tarnish, or at least make them.

This Structure I somewhat the more diligently survey'd, because I could not well comprehend, how, if there were such a glutinous matter in those supposed Sponges, as most (that have observ'd that Object in a _Microscope_) have hitherto believ'd, how, I say, the Fly could so readily unglew and loosen its feet: and, because I have not found any other creature to have a contrivance any ways like it, and chiefly, that we might not be cast upon unintelligible explications of the _Phaenomena_ of Nature, at least others then the true ones, where our senses were able to furnish us with an intelligible, rationall and true one.

Somewhat a like contrivance to this of Flies shall we find in most other Animals, such as all kinds of Flies and case-wing'd creatures; nay, in a Flea, an Animal abundantly smaller then this Fly. Other creatures, as Mites, the Land-Crab, &c. have onely one small very sharp Tallon at the end of each of their legs, which all drawing towards the center or middle of their body, inable these exceeding light bodies to suspend and fasten themselves to almost any surface.

Which how they are able to do, will not seem strange, if we consider, first, how little body there is in one of these creatures compar'd to their superficies, or outside, their thickness, perhaps, oftentimes, not amounting to the hundredth part of an Inch: Next, the strength and agility of these creatures compar'd to their bulk, being, proportionable to their bulk, perhaps, an hundred times stronger then an Horse or Man. And thirdly, if we consider that Nature does always appropriate the instruments, so as they are the most fit and convenient to perform their offices, and the most simple and plain that possibly can be; this we may see further verify'd also in the foot of a Louse which is very much differing from those I have been describing, but more convenient and necessary for the place of its habitation, each of his leggs being footed with a couple of small claws which he can open or shut at pleasure, shap'd almost like the claws of a Lobster or Crab, but with appropriated contrivances for his peculiar life, which being to move its body to and fro upon the hairs of the creature it inhabits, Nature has furnish'd one of its claws with joints, almost like the joints of a man's fingers, so as thereby it is able to encompa.s.s or grasp a hair as firmly as a man can a stick or rope.

Nor, is there a less admirable and wonderfull _Mechanism_ in the foot of a Spider, whereby he is able to spin, weave, and climb, or run on his curious transparent clew, of which I shall say more in the description of that Animal.

And to conclude, we shall in all things find, that Nature does not onely work Mechanically, but by such excellent and most compendious, as well as stupendious contrivances, that it were impossible for all the reason in the world to find out any contrivance to do the same thing that should have more convenient properties. And can any be so sottish, as to think all those things the productions of chance? Certainly, either their Ratiocination must be extremely depraved, or they did never attentively consider and contemplate the Works of the Al-mighty.

Observ. x.x.xVIII. _Of the Structure and motion of the Wings of _Flies_._

The Wings of all kinds of Insects, are, for the most part, very beautifull Objects, and afford no less pleasing an Object to the mind to speculate upon, then to the eye to behold. This of the blue Fly, among the rest, wants not its peculiar ornaments and contrivances; it grows out of the _Thorax_, or middle part of the body of a Fly, and is seated a little beyond the center of gravity in the body towards the head, but that _Excentricly_ is curiously balanc'd; first, by the expanded _Area_ of the wings which lies all more backwards then the root, by the motion of them, whereby the center of their vibration is much more backwards towards the tail of the Fly then the root of the wing is. What the vibrative motion of the wings is, and after what manner they are moved, I have endeavoured by many trials to find out: And first for the manner of their motion, I endeavoured to observe several of those kind of small Spinning Flies, which will naturally suspend themselves, as it were, pois'd and steady in one place of the air, without rising or falling, or moving forwards or backwards; for by looking down on those, I could by a kind of faint shadow, perceive the utmost extremes of the vibrative motion of their wings, which shadow, whil'st they so endeavoured to suspend themselves, was not very long, but when they endeavour'd to flie forwards, it was somewhat longer; next, I tried it, by fixing the leggs of a Fly upon the top of the stalk of a feather, with Glew, Wax, &c. and then making it endeavour to flie away; for being thereby able to view it in any posture, I collected that the motion of the wing was after this manner. The extreme limits of the vibrations were usually somewhat about the length of the body distant from one another, oftentimes shorter, and sometimes also longer; that the formost limit was usually a little above the back, and the hinder somwhat beneath the belly; between which two limits, if one may ghess by the sound, the wing seem'd to be mov'd forwards and backwards with an equal velocity: And if one may (from the shadow or faint representation the wings afforded, and from the consideration of the nature of the thing) ghess at the posture or manner of the wings moving between them, it seem'd to be this: The wing being suppos'd placed in the upmost limit, seems to be put so that the plain of it lies almost _horizontal_, but onely the forepart does dip a little, or is somewhat more deprest; in this position is the wing vibrated or mov'd to the lower limit, being almost arrived at the lower limit, the hinder part of the wing moving somewhat faster then the former, the _Area_, of the wing begins to dip behind, and in that posture seems it to be mov'd to the upper limit back again, and thence back again in the first posture, the former part of the _Area_ dipping again, as it is moved downwards by means of the quicker motion of the main stem which terminates or edges the forepart of the wing. And these vibrations or motions to and fro between the two limits seem so swift, that 'tis very probable (from the sound it affords, if it be compar'd with the vibration of a musical string, tun'd unison to it) it makes many hundreds, if not some thousands of vibrations in a second minute of time. And, if we may be allow'd to ghess by the sound, the wing of a Bee is yet more swift, for the tone is much more acute, and that, in all likelihood, proceeds from the exceeding swift beating of the air by the small wing. And it seems the more likely too, because the wing of a Bee is less in proportion to its body, then the other wing to the body of a Fly; so that for ought I know, it may be one of the quickest vibrating _spontaneous_ motions of any in the world; and though perhaps there may be many Flies in other places that afford a yet more shrill note with their wings, yet 'tis most probable that the quickest vibrating _spontaneous_ motion is to be found in the wing of some creature.

Now, if we consider the exceeding quickness of these Animal spirits that must cause these motions, we cannot chuse but admire the exceeding vividness of the governing faculty or _Anima_ of the Insect, which is able to dispose and regulate so the the motive faculties, as to cause every peculiar organ, not onely to move or act so quick, but to do it also so regularly.

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 c.o.c.k, which by vibrating to and fro, might, as 'twere, open and shut the c.o.c.k, and thereby give a pa.s.sage 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 pa.s.sages 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 _a.n.a.logous_ 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 Gla.s.s, 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 b.u.t.terflies 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 surpa.s.sing beauty, as is evident enough to the naked eye, in the painted wings of b.u.t.terflies, but much more through an ordinary _Microscope_.

Intermingled likewise with these hairs, may be perceived mult.i.tudes of little pits, or black spots, in the exended 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 mult.i.tude 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 mult.i.tude 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

Observ. x.x.xIX. _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 cl.u.s.ters 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 k.n.o.bs or b.a.l.l.s of each cl.u.s.ter, 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 mult.i.tude 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 a.s.sured 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 mult.i.tudes 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, Gla.s.s, 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-gla.s.s 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 _circ.u.mspect_. 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 k.n.o.bs, 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 cl.u.s.ters 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 cl.u.s.ter 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 cl.u.s.ter, 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 Sh.e.l.l-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 quant.i.ty, 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 cl.u.s.ters, 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 cl.u.s.ters 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 k.n.o.bs, 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 k.n.o.bs 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.