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that once were enclosed in the moutonnéd ridges, and subsequently eroded therefrom. The gold is believed to be in quantity sufficient to be profitable to mining operations, especially because the mining could be done economically by water, which is convenient, abundant, and has a rapid fall or descent in the nearby creeks.

The alluvial beds of auriferous clays, sands, gravels, and small boulders that are found in the beds of some of the gulches and in the channels of some of the present system of creeks are often partly cemented by hydrous oxide of iron in some places and by silica at other localities. These deposits were commenced, I am persuaded, during the Terrace epoch, and, in some places, are apparently quite rich in gold of rough, semi-angular pieces and in rounded particles; yet some of the particles of gold in the small creeks or nearby dry gulches appear so angular and undisturbed at their edges as to impress one with the opinion that they have increased in size, "grown," where they are discovered by additions from passing solutions containing gold; the chief sources, however, of the gold found in these creeks are the same as those named under the head of reefs or lodes, with additions of gold from the older leads above described found in the upper, and apparently passing through the erosion-formed hills and from accretions of gold deposited from passing auriferous solutions. The bedrock in some of the creeks is an iron-cemented arenaceous argillyte resting on a bed of partly cemented boulders, sands and clays which appear, at one place discovered, probably in the entire locality, to rest on strata of auriferous conglomerates or breccia and this on an auriferous gravel superimposed on a bedrock of metamorphosed shale or slate.

Geological history. We found several obstacles intervening to prevent, at present, that careful examination necessary to determine the geological epoch, when these granite ridges were upheaved and when thereafter they were exposed by the denudation of superimposed strata; during what epoch the regional elevation occurred and the erosion-sculptured hills in that region were formed; from what rocks or sources came the gold found now in the reefs or lodes traversing, longitudinally, the mountains and ridges.

One obstacle is that no ravines or cañons were discovered that deeply enough expose the strata toward the centre of the mountains or ridges.

Other obstacles are, the very deep disintegration, in situ, of the exposed rocks and the deep soil covering the surface and also the dense vegetation, frequently a jungle difficult to cut a pathway through, covering in matted masses even the nearly perpendicular sides of ravines; but, tentatively, and from the clearest examinations we could make, we form the following geological history of this locality.

1. The granite in the hills and ridges was forced up through Jurassic period and later rocks and it upturned to nearly vertical the superimposed strata, in some of which strata were discovered moulds of silica (lined with small crystals of quartz) like the Trigonia Conradi, also others like moulds of Tancredia Warreniana.

The fissures, also the dykes of diorite, appear to have resulted from disturbances occurring in epochs PostOolitic, but not extending later than the Cretaceous, this being the latest known or generally recognized time or period during which gold has been conveyed in large quantities or percentages, as a constituent in granites and diorites, up to the earth's crust; these auriferous granites and diorites are certainly abundant in this region and are not Palæozoic nor Cenozoic rocks. The gold in the reefs

or lodes has been dissolved from the granites and diorite rocks by hot mineralized waters and deposited

therefrom into the fissures or reefs, on cooling or on deoxidation of the solutions, either enclosed in pyrites or as free gold.

The gold in the placer mines, drifts or leads, appears to have been derived almost entirely from the disintegrated and denuded granites forming the mountains and from the reefs in the mountains; a small percentage of the alluvial gold is, however, from the small areas or patches of auriferous quartz eroded from the moutonnéd ridges, also a small percentage of gold has been deposited from passing alkaline waters that contain gold in solution.", ".

The patches of auriferous quartz found generally at the base of the moutonnéd ridges as if eroded from them appear to have been transported (with the other materials composing the moutonnéd ridges) from auriferous reefs in the ridges forming the southeastern part of the Matagalpa system of mountains.

The boulders of bluish-colored rocks, auriferous and containing a large percentage of pyrites, found quite frequently in that region, are usually some variety of the soda-bearing hornblede rocks like glaucophanyte, although bluish trachytes, also bluish hypersthene boulders, some of them auriferous (probably all of them) were discovered. Some of the very interesting observations noted. were: (a) The altitude above the Caribbean Sea (aneroid readings) of several of the hills and ridges in the region herein described is from 1,000 to 3,600 feet, consequently the flow of water to the Caribbean Sea, only 90 or 100 miles distant, is very rapid, there being no swamps, only those of brackish water in the delta of the rivers; this rapid descent of water from the mountains over numerous rapids, cascades and falls in the creeks and rivers offers many places where great water power or pressure could be had to move machinery for sawing logs, defibrenating plants, mining, etc.; (b) That region, excepting the claysurfaced moutonnéd ridges, is covered, from two to twelve or more feet deep, with a very fertile soil composed in large percentage of partly decomposed vegetable matter (nitrogenous) and potash and other alkalies and alkaline earths, from the alkali-containing rocks, granite, feldspar, etc. Consequently there are excellent agricultural lands for corn, potatoes, coffee, tobacco, almonds, etc., on the sides of the hills and ridges, and suitable for sugar cane, plantains, bananas, cacao, India rubber trees, etc., in the valleys. Some of the mountain lands are admirable for coffee, and in the upper valley lands, indigenous cacao trees (Theobroma) of good varieties are numerous; (c) The climate is warm, but not uncomfortable, no lagoons nor swamps in the hilly region; (d) On the mountain ridges grow forests of large trees, among which mahogany, cedar, rosewood, sapote (Ulva sylvestra), iron wood, guanacaste and nispero appear to be the most nu

merous.

The tunoo trees' are also numerous and of large size, and, young vigorous-growing India rubber trees (Syphonia elasticos) are very abandant, while in shaded moist places, the surfaces of disintegrating rocks are frequently covered with the beautiful velvet vine of Nicarragua (first discovered about 1856 in Nicaragua), having

Gold being invariably found in the granitic series of rocks, especially those of Paleozoic and Mesozoic eras and early Tertiary period, should, I am inclined to believe, influence us to recognize the gold as a constituent and not merely an accessory mineral in the rock.

The fact of the existence of gold in rocks of the granite series appears to give support to the theory of the successional deposition of the elements in the earth, those of greatest sp. gravity being nearest to the earth's centre. Platinum, gold and iron appear to have been brought to the crust of the earth in every upheaval of granitic masma.

The tunoo exudes freely, when scarified, a milky juice appearing like the milk or sap that flows from lacerations in an India rubber tree, but concretes into a gum like gutta percha. The fibrous inner bark is a texture of strong interwoven fibres and can be removed from the tree in pieces as wide as the circumference of the tree (from three to six or six and a half feet wide) and twenty to forty feet long. The Soomoos and Sambos use this bark as bedclothing and as clothing for their bodies; they prepare the bark for these purposes after removing it from the tree by wetting in water and softening by beating it with sticks, when it becomes soft and remains very strong.

its exteriorly pure, white, trumpet-shaped, velvety flower tinted with various clear colors of purple, golden, pink, etc. Orchids in great variety are numerous, also ferns of all sizes, up to trees twenty feet high, are abundant.

This wilderness contains much undeveloped wealth in its export varieties of trees, medicinal and fibrous plants, and in its undeveloped minerals, metals, and very fertile agricultural lands, and has much to interest scientists, especially naturalists.

July 30.

A NEW REFLECTING AND DIRECT ACTING POLARISCOPE FOR THE ARC LIGHT PROJECTOR.

BY OSCAR KNIPE, PHILADELPHIA.

REFERRING to a paper on the subject of Projection, published lately in Engineering and several other periodicals, it was then indicated that most of the accessory instruments for Projection, among them the polariscope, would become more popular and find increased employment in the various courses of instruction. The arc light being so convenient, prompt in application and so perfectly satisfactory, suggests, of course, an extended application, and in consequence the expert will frequently find chances for improvement.

The favorite construction of the polariscope has been with Nichol's Prisms, two of these being employed, one for the polarizer and the other for the analyzer. To obtain brilliant effects it is necessary that the former should be at least two inches across the face; unfortunately it is now impossible to obtain such large crystals of spar, and as the demand for these instruments increases very much the reflecting polariscope again comes to the front; the old elbow arrangement furnished by some makers of instruments is a very clumsy attachment and inconvenient, as it requires the projector to be turned side-ways so that the light can reach the screen in front of the audience.

Various modifications have been proposed mainly by London makers and amateurs to obtain a direct acting reflecting polariscope by two opposite surfaces set in a box at the usual angle and deflecting the beam upward or downward, but the main objection, that of being inconvenient, still remained. The optical bench of the Paragon Projector offers, however, special advantages in that respect; the distance from the centre of the arc to the slide base being sufficient to allow a downward polarizer to be adopted, leaving abundant room for the object stage, objective and analyzing prism upon the bench. In practice this instrument is found to be simple in adjustment with the light, and the results obtained are surprising; the field projected is perfectly circular and even, alternating it light and completely dark by rotating the analyzer. The object stage here used is a novel devise; it consists of two uprights which open and close by a spring forming a clamp, a rotating ring with spring clips is secured to each clamp upright, so that three objects can be combined at one time, which is required for circular and eliptic polarization. The stage for exhibiting the phenomena of polarization in crystal, glass forms (verre trempe), and those produced by heating the object will be described at a future time.

The polariscope described above is specially adapted for plane and circular polarization of geometric and fancy designs of Selenite and Mica. The latter is easily obtainable and can be split into laminæ of various thicknesses, the thinnest that can be taken off in a square of about two inches is technically known as an eighth wave plate, the next thickness equal to two oneeighth films superposed is termed a quarter wave film and another equal to two one-quarter films superposed is the half wave film. The quarter and half wave films are

the most useful in producing the most marvellous color combinations imaginable, not only in the gay primaries of the solar spectrum, but also in the more quiet grays and plain colors generally; taking a specimen composed of four or six strips of selenite about one-quarter of an inch wide by one and a quarter inches long, laid closely together, it will project its primary colors at once upon the dark field obtained by the position of the analyzer; the slightest turn to the right or to the left produces a change in the colors, but if we move the prism through one-quarter of a revolution the field is changed to a ground flooded with light and the colors have respectively changed to their complementary tint, the carmine has become a pale green, the lemon color an azure blue and so on; they are termed complementary because when superposed they produce white light. Allowing the specimen to remain, we take advantage of the rotary slip in front of our triple object stage and place there another specimen of selenite strips exactly like the first, but place it at right angles or diagonally and we now will have an illustration of the fact alluded to that complementary colors produce white light. The reason that only here and there a square or diagonal of real black or white is produced is found in the difficulty in matching exactly the films. After passing through the various changes, taking a note perhaps of the exact angle at which a certain color is produced so as to be able to repeat it afterward, we will remove the specimen from the front of the stage, and replace it by a quarter wave film; these have generally the axis marked on the edge by an arrow. We shall now obtain a decidedly different set of colors, which con be varied by rotating the analyzer; but notice now that instead of the two complementary colors we have a continual interchange of four or more colors, which can all be registered and repeated. When the quarter wave or half wave film is placed on the rotary clip at the back and rotated we obtain a different set of colors as well as

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a colored background. A specimen representing three or four concentric circles, or a wheel divided into a number of sections joining at the centre or again a thin slab of selenite which is ground concave on its face, either of these will give the most beautiful and fascinating changes of color. As these various types of colors are absolute standards taken from the book of nature which can be exhibited precisely alike, it is obvious that we have here in this branch of polariscope study the most brilliant, complete and unchangeable system of color samples with their complementaries and color contrasts which far surpass any book of artificial colors. These when projected on the screen in a class become the objective point of every member, and can be pointed out, and commented upon by the instructor. As the geometric designs may be varied in composition, the mica films being very inexpensive, it requires merely a little patience and experience to produce an unlimited variety. The apparatus described in this article is made by Queen & Co. Incorporated of Philadelphia.

THE SENSE-ORGANS ON THE LEGS OF OUR WHITE ANTS, TERMES FLAVIPES, KOLL.

BY DR. ALFRED C. STOKES, TRENTON, N. J.

In an eyeless creature that habitually shuns some influence in the light, and lives in subterranean passages, or in tunnels or dark fissures within decaying wood, we should hope and rather expect, if we considered the matter solely from the human standpoint, to find either an extra number of sense-organs or a supply of an unusual variety, as a compensation for the absence of sight and for the limitations of a restricted environment. Such human expectations would be realized in the case of the white ants, Termes flavipes, so common within the rotting stumps and the fallen branches of our damp woods, for these Platyptera possess what may be considered to be an ample exchange for sight, for they have on all of the six legs a wonderful number and variety of sense-organs, which should certainly meet the needs of a peculiar life, as they doubtless do.

It is generally agreed among naturalists that certain insects, perhaps the greater number, possess some senses different from any owned by man and of which we therefore can have no idea. Sir John Lubbock says, "It is, I think, generally assumed, not only that the world really exists as we see it, but that it appears to other animals pretty much as it does to us. A little consideration, however, is sufficient to show that this is very far from being certain, or even probable."

On each of the legs of Termes flavipes there are seven organs which are plainly sense-organs, with three forms of appendages which may be sensory, but are probably ornamental only. The blind, subterranean Termes, then, with six legs and with seven sense-organs on each, is right well. prepared for whatever whatever may happen, even for the forceps of the predatory microscopist. The forceps conquers in the end, but the insects seem to feel its presence before it touches them, retreating and sometimes backing away from it as from some obnoxious object. Yet upon this apparent fact I should put no great reliance, as the observation was made with a single nest and late in the season, although the lateness of the season would probably have no effect, except to render impossible, as it did, a repetition of the experiment. It may, therefore, have been an event "viewed unequally.”

The appendages referred to as being doubtfully sensory are mere elevations of the chitinous walls, ornamental in their arrangement, minute in size, and if possessing any special nervous connections, these have escaped my notice. The appendages, or ornaments, vary much in appearance on the coxa, the trochanter and the tarsus, the femoral and the tibial ones being similar to those on the coxa. On the latter the elevations are simply aculeate, the aculei being exceedingly minute; on the trochanter and on the femur they take the form of minute prickles, which, at first glance, appear to mark out the impressions of the chitinogenous cells, as in Fig. 1, from the femur; on the tibia the elevations become still more aculeate (Fig. 2); they are more widely separated, and the delicately elevated ridge which bears them gives the markings much the aspect of irregular, thick-edged scales, especially at the distal extremity, as in Fig. 3; on the tarsus the change from these clusters of aculei is abrupt, more or less semicircular scales, with thickened and elevated margins taking their place, as in Fig. 4, the edges of these being sometimes minutely denticulate. Viallanes, speaking of the situation of the sensory hairs of insects in reference to the chitinogenous cells, says that there are "two kinds of hairs, distinguished by their size and structure. The smaller spring from the boundary between contiguous polygonal

areas, and have no sensory character. The larger ones occupy unusually large areas, surmount chitinogenous cells of corresponding size, and receive a special nervous supply." It is more than probable, therefore, that these minute appendages have in no place a significance different from that possessed by the minute elevations so common on the exo-skeleton of so many insects. But to notice the different form and arrangement on the different portions of the leg is at least interesting and suggestive.

The chitinous bristles, or "hairs" (Fig. 6), have here the usual form, and the structure described by Viallanes, being slightly constricted at base and inserted in a hemispherical depression as a socket-joint, and furnished with a nerve-fibre, of which Viallanes says: "The nerve expands at the base of the hair into a spindle-shaped, nucleated mass (bipolar ganglion-cell), from which issues a filament which traverses the axis of the hair, piercing the chitinogenous cell, whose protoplasm surrounds it with a sheath which is continued to the tip of the hair. Such sensory hairs are abundant in parts which are endowed with special sensibility."* On the legs of Termes flavipes these are, as elsewhere, sense-organs of great delicacy, with a sense of touch probably as sensitive as that of man himself.

In the same list with these sensory hairs may be mentioned organs of a similar character and of apparently great importance to the insect, which are found at the distal extremity of each tibia, each leg of the second and of the third pair bearing two, while those of the first pair have three. They are stout thorns, or spurs, projecting, in the first or anterior pair, two from the lower lateral margin of the tibia, with one from the upper lateral border, as shown in Fig. 9, where the other sensory hairs have been omitted.

They are conical organs, measuring about 1-450 inch in length, and are, during life, well supplied with nervesubstance. But that which gives them their unique character is the presence of a more or less circular aperture near the basal or tibial portion of the thick wall, as shown in Fig. 9, and more in detail by Fig. 15, each insect thus possessing no less than fourteen of these peculiar perforations. The circular aperture is externally surrounded by a thick-walled, elevated, marginal ring, and across it, apparently at the level of the general surface of the tibial wall, extends a delicate membrane, supplied with a rather conspicuous, centrally disposed nerve-fibre, as shown in Fig. 15, where a nerve is also delineated as passing from the tissues within the hollow of the spur to the mass of nerve-tissue which is here retracted from the walls, probably by the processes of preparation. Within the mass thus withdrawn ganglion-cells are plainly visible.

What may be the function of these fourteen organs, which are doubtless sense-organs of importance, must be left to the reader to explain. I do not know that they have been previously observed; yet it is more than possible that I may have overlooked some parts of the scattered literature of the general subject. If any plausible conjectures have been published in regard to the function of these or of similar organs, I should be pleased to know what they are, although all such statements must necessarily be conjectural. It is easy to state that certain depressions on the antenna of a bee are auditory or olfactory, but it is quite another matter to do more than to make the assertion. When it comes to the making of experiments to learn the actual function of these minute structures, the obstacles met with are practically insurmountable. But if these tibial spurs of the white ants, with their prominent basal apertures, have been previously studied, and if any probable guessing has been done as to

*Cf. "The Cockroach," by Miall and Denny, p. 30.

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their character, I should like to know at what result the philosophical observers have arrived.

At first glance the organs might be supposed to be auditory, on account of the membrane, which closes them, and the only reason for rejecting such a supposition is that I have not seen any trace of the staff-like rods or the pyriform bodies which Graber found so well developed in what could not be imagined to be anything but organs of hearing in the tibia of the locust, Locusta viridissima, and of some other members of the same, or of an allied, order. The auditory organs of our white ants seem to be in an entirely different position and of an entirely different structure.

On the outer wall of the upper, or coxal, end of the trochanter is a group of just seven conical, setose and colorless hairs, surrounded by a circumvallate base, and on the upper outer wall of the coxa is another group of similar hairs, always ten in nnmber, and, presumably, having the same function. These groups are entirely absent from the inner walls. To show its locality, the cluster is exhibited on the trochanter by Fig. 10, and greatly enlarged in Fig. 11.

sides, and are sparingly scattered over the surface of the tibiæ. In Figs. 10 and 11 their general form and usual position and arrangement are shown, although in these particulars they are not constant. The number is also uncertain within known limits, varying on the outer side of each trochanter from thirteen to fifteen, thirteen being the common number; on the femur two and on the upper lateral wall of the tibia, from two to five, with sometimes an unusually large subcentral one, similar to a large one on the inner wall of each tibia; the inner walls of each trochanter also bear from four to five; on the upper part of the femur are from three to four; the central tibial surface has one, and one is near the lateral border of the distal extremity of the tibia.

In structure they closely resemble the circular apertures at the bases of the tibial spurs, each consisting of an elevated ring, having, at the level of the general surface, a delicate membrane furnished with a nerve-fibre, which elevates the centre into a minute but conspicuous papilla. These points are shown in Figs. 5 and 7, the latter being an optical section of a pit.

On the trochanters these organs are arranged somewhat

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Fig. 1, surface markings from the femur; Figs. 2 and 3, from the tibia; Fig. 4, from the tarsus; Fig. 5, sensory pit from the tibia; Fig. 6, sensory hair from the general leg-surface; Fig. 7, optical section of a sensory pit; Fig. 8, pílose depressions on the lower end of the tibiæ; Figs. 10 and 11, sensory hairs, pits and hooded pits on the trochanters; Fig. 12, tibial trachea, with recurrent branch; Fig. 13, position of supposed tibial auditory organ; Fig. 14, pits on the lower surface of the first and second segments of the tarsus, one filled with crystalline excretion; Fig. 15, sensory pit at the base of a tibial spur; Fig. 16, tibial auditory organ, partly diagrammatic. All the figures are much enlarged.

These hairs differ widely in size, form, and general aspect from the sensory bristles of the general leg-surface. Underlying them is a specialized group of nerve-cells, which supplies each with a fine nerve-filament.

It is a fact worthy of note that these and other senseorgans are on the outer wall of the various parts of the legs which bear them, and that they either have no representatives on the surface toward the insect's body, or are there smaller and in much less abundance. Even the large sensory hairs of the general leg-surface are much fewer on the inner aspect of the legs.

In addition to these setose appendages, each trochanter bears other sensory organs, which take the form of elevated, circular, or oval rings, surrounding apertures of the same form in the thickness of the walls, some being capped by a conical, often oblique, hood-like membrane. They, as usual, are found chiefly on the external walls of the trochanters, but exist in fewer numbers on the inner

in three groups, according to size, and the three or four largest, resembling flat-topped papilla pierced with a central depression above the membrane, frequently become confluent, those of the other two groups being capped by a conical, often oblique, hood-like membrane, as shown in Fig. 11. These hooded apertures bear some resemblance to the "canoe-cells" of certain authors, and which are said by Huxley to be only ordinarv pits overarched by a fine hair. In the present case, however, there is no arching hair, but a distinct hood-like elevation, which is especially conspicuous on the trochanters of the soldier.

It is reasonable to suppose that the capped depressions have a function differing from that of the flat-topped papillæ on the same surface. Those without the hooded covering seem analogous to the sensory pits discovered on the antennæ of certain plant-lice by Dr. John B. Smith, of Rutger's College (Science, Jan. 20, 1893). A rather hasty

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examination of the antennæ of the white ants does not reveal pits of any kind on the surface, although I am not prepared to say that they are not there. Dr. Smith also found on the posterior tibiæ of the plant-lice a series of the pits, exactly similar in structure, he says, to those of the antennæ in the male. Their function in Termes flavipes is as problematical, as Dr. Smith remarks in reference to the sensory pits of the plant-lice. They are present in both the workers and in the soldiers of the white ants, varying in the latter as they vary in the workers.

Perhaps the most interesting of these sense-organs, by reason of their position and of their probable character, are certain depressed spaces, several of which are on the tibiæ, and one on each of the first two segments of the tarsus, where the parts come in contact with the surface over which the insect may walk. With every step taken, these sense-organs perform their work, and probably leave on the surface walked over traces of the presence of their owners, as may readily be imagined, to impress the senses of those that follow. In all this remarkable collection of sense-organs there is none that seems to explain so clearly its reason for being as do these. Yet my supposition that they leave some special evidence of their owners' former presence which shall be manifest to the other members of the insect community, is based upon the observation of appearances in the tarsal organs of some individual Termes which are not apparent in those of others. This is that the deep depressions always present on the first and second segments of the tarsus are sometimes filled with a crystalline mass, which projects beyond the general surface as a hemispherical protuberance, especially, as it now seems, late in the season, and with presumably old subjects, thus suggesting the idea that the tarsal organs, at least, are glandular in function, and that the crystalline substance is the hardened secretion collected through abnormal, or sluggish, action of the parts.

On the tibiæ the organs referred to are shallow depressions in the wall, bordered by thickened margins, and with the plane surface of the shallow studded with delicate, exceedingly minute hairs, whose tips project slightly beyond the general level, and necessarily come in contact with any surface over which the insect may walk. The tibial depressions, while they are always present, are not always of the same outlines or of the same number. In some instances there may be one large depression with several small ones scattered about, as in Fig. 8, or the single large depression may be divided into several smaller portions, which shall be scattered over the region without any regularity of arrangement.

On the first and second segments of the tarsus the organs are always present, and always in the same position on the surface which must come in contact with the ground. Each of the two segments bears one in the form of a thickwalled, deep, hemispherical pit, the smooth inner surfaces of which are also studded with fine hairs similar in appearance to those of the tibial depressions, and with presumably the same functions. It is these hollows that are in many specimens choked with the crystalline excretion already referred to, and shown in Fig. 14, where one pit is filled and the other apparently in its normal condition. is plentifully supplied with fine nerve-fibres. Not rarely there are two pits, instead of one, on one or the other of the two segments; in a single instance, I have seen three on the second joint. But these hairy hollows deserve more extended investigation by some microscopist that may be more conveniently situated for that work than I am, and that may have the resources of a laboratory at his disposal.

Each

To such an investigator, thus fortunately situated, the internal structure of these remarkable legs will also offer important subjects for examination. This is especially true of what I suppose, for reasons to be mentioned here

after, to be the insects' auditory organs, one being present in each tibia, a supply of internal ears that would seem to be more burdensome than necessary or agreeable. (Fig. 13.)

It is possible that these organs may have some connection with the trachea, although that connection cannot be close; yet here, as in some other insects, the tibial tracheæ are specially notable on account of the sac-like enlargement of the upper and of the lower ends of the main tube, and of the presence of a smaller, recurrent branch, which leaves the upper inflated portion to enter near the lower at a varying distance from the extremity. This structure has been observed in the locust (Locusta viridissima), the cricket (Gryllus campestris), and in various Orthoptera by Graber; while Sir John Lubbock describes a similar arrangement in the tibia of the ants, especially in Lasius flavus. This tracheal structure is well developed in all the tibia of Termes flavipes, varying in the length of the recurrent branch and in the more direct or more undulating course of the main trunk of the trachea. In Fig. 12 is shown the appearance in one of the tibiæ of the white ants.

In the locust (Ephippigera vitium Serv.), according to Graber, and in certain other Orthoptera, the main tracheal trunk bears a collection of ganglion-cells and globules supposed to be auditory in function, at least in part, and which, if present in Termes flavipes, have escaped my notice. Yet in each tibia of this insect, situated near the outer wall of each, between it, the nerve and the trachea, is the more or less ovate organ referred to, the structure of which bears considerable resemblance to that of what has been accepted as a tibial auditory organ in certain of the Orthoptera. Its position near the upper third of the tibia of Termes flaviges is shown in Fig. 13.

It is connected with the nerve, and is itself formed of a collection of ganglionic cells and globules, with plainly developed, staff-like bodies, the apical extremities of which are conical, and through the middle of their apparently hollow length passes what seems to be a fibre, presumably a nerve. The external extremity is continuous with a nerve-fibre, five of which, with as many elongated, stafflike bodies, being easily made out, the nerves passing singly and separately up toward the femero-tibial joint, near which they are lost to view, especially after my imperfect methods of preparation.

Similar organs have been discovered by Graber in the tibiæ of the Locustidiæ, and by Lubbock in those of certain ants. In reference to the latter, Lubbock says: "At the place where the upper tracheal sac contracts there is, moreover, a conical striated organ, which is situated at the back of the leg, just at the apical end of the upper tracheal sac. The broad base lies against the external wall of the leg, and the fibres converge inwards. In some cases I thought I could perceive indications of bright rods, but I was never able to make them out very clearly. This also reminds us of a curious structure which is in the tibiæ of the Locustid æ, between the trachea, the nerve, and the outer wall. On the whole, then, I am disposed to think that ants perceive sounds which we cannot hear." In Termes flavipes its position is somewhat different, although its situation and its structure are essentially similar to those referred to by Lubbock and by Graber. It is an organ of fibres, of ganglionic cells and globules, the latter being large and nucleated, and of the long, stafflike bodies already referred to. A partly diagrammatic sketch of the organ is shown in Fig. 16, its outer, narrow extremity being attached to the wide nerve just within the external wall of the tibia and the broad base directed toward the external wall of the trachea.

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The rod-like bodies bear a rather remote resemblance to some observed by Graber, in what he considers to be

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