er, on their combustion for the musical sounds that they emit, must, it appears from Count Schaffgotch's and Prof. Tyndall's wellknown experiments, when placed in certain circumstances of $72 silence and indifference in an open tube, be aided by the voice at a distance to commence their song. The signal-note first raises certain mechanical vibrations in the gas-current of the narrow jet, that are necessary in the outset to produce commotions enough of the singing flame to make it able to continue and maintain them. The sensitive sounding-flame of Mr. Geyer bears a similar explanation, for not being regularly adjusted, although very nearly so, to continued sounding, a rustle sufficient to flurry the sensitive wire-gauze flame under the open tube creates in it so many brisk explosions, that the resonance of the sounding-tube is excited, and is at once exalted to a loud note by the rhythmical expansions of the flame; but with the cessation of the external sound the maintaining impulse ceases, and the wire-gauze flame whose commotions must be kept up in order to maintain the note immediately becomes as silent as before. 10 on rd 0. 2 er d 13 It is remarkable that the gas-pressure used to obtain Barry's sensitive flame is not sufficient to produce visible sensitiveness in the taper-jet alone; but if the gauze is raised and lowered over the unlighted jet, a proper position is soon found where the cone of blue flame burning on the gauze above possesses a very high degree of sensibility. The use of smoke-jets instead of flames in this arrangement would perhaps give more positive proofs than may yet have been obtained of the cause of the impressibility. It appears, however, scarcely probable that in the short space of a few inches from the aperture the pin-hole current of unlighted gas can increase its amount of air-mixture so much by the influence of external sounds, that this would account sufficiently for the descent of the conical gauze-flame from the pretty stately eminence of a tall and steadily-burning hill top, to little more than the elevation of a stormy bed of low struggling and bustling flame. The alternative supposition is that the disturbance commences in the meshes of the gauze itself, and that it extends upwards from them with such rapidly increasing agitation that a perfect mixture of the gas-current with the surrounding air, and its complete combustion, are thus enabled to take place at very short distances above the gauze. I have been led to offer these few reflections on some of the most remarkable examples of sensitive and sounding flames from a wish to distinguish in their action as well as possible between the part which purely mechanical forces, and that which the operations of heat and combustion play separately in their production. The mechanical part of the explanation appears to consist in supposing the sensitive jet, when it is properly ad justed, as being in a state either bordering upon, or of actually existing undulation. The hissing sound of all air-jets, if listened for attentively enough, is a proof of the reality of the disturbance; and such sounds, it has been suggested by Sir G. Airy, indicate disruptions of continuity in the air round the nozzle of the jet, arising, no doubt, from the rapidity with which particles of the quiescent external air are there carried off by friction with the gas-current of the jet. It is hardly possible that vacua so complete (when they exist) should fail to supply the jet with a succession of smoke-rings encircling it and probably travelling up the jet with different speeds according to their magnitude and the depth to which they are involved in the upward current of the gas. If a disposition to regular periodic action exists in the jet (and the smoother its orifice, and the more steady the supply of gas to the jet, the more probable this appears to be), a succession of smoke-rings of the same size, and of greater or less strength according to the uniform pressure of the gas, may easily be supposed to course each other up the flame, and being gradually consumed in ascending, to leave its tall column to the top with sides as smooth and even as a rod of glass. But if the gaspressure is much increased, a phenomenon like that of companion cyclones observed in rotating storms, perhaps presents itself at the orifice of the jet, each strong smoke-ring as it is formed being * * The word "smoke-rings," as here used occasionally, is not intended to imply the presence of smoke in the jet or flame, but to denote by a familiar phrase an annular air-vortex having its rotation round a circular line or ring of lower pressure than that of the surrounding air. Such annular vortices are most easily seen in liquids by drawing a flat blade through them with its broad side in front; or, indeed, as was lately shown to me by Prof. James Thomson, who supplied me with their explanation, in a cup of tea, by drawing a spoon very gently through it. Only half of the annulus is formed, encircling the edge of the blade or spoon with a curved line of low pressure, round which the liquid spins as in a smoke-ring, and shows a little whirlpool on the surface, one at each point of intersection of the surface with the low-pressure line below it. If an oar-blade is drawn rather rapidly through water, groups of two or three of these ring-vortices following each other in its track can very readily be produced. probably followed by a weaker one (a residual offset from the first) travelling after it with less velocity on the outer surface of the flame. The companion rings are probably overtaken and destroyed at a certain height in the flame by the next following strong ring, and the succession being continuous, a puff at a certain height in the flame, where the companion rings collapse, throws it there into a permanent excrescence or confusion. Both rings may be broken by the shock, and if of oval forms, as they must probably be in some jets, the two projecting halves of the stronger ring when struck, on springing outwards may thus appear to divide the flame at a certain height above the jet into two pointed tongues forking outwards from each other to a certain width. This form of sensitive flame was shown to be readily obtainable by Prof. Barrett by means of a tapering glass quilltube jet, the edges of which on two opposite sides are slightly ground or snipped away into a V-shaped notch. Besides the secondary or companion ring, tertiary and higher orders of fol lowing rings may possibly be formed; and each strong primary ring may have to run the gauntlet of several weaker antagonists before it at last emerges safely, or else is destroyed itself in its conflicts with them. The flame is lowered to a bushy head in the latter case; but if the primaries outlive their shocks, and if, as might sometimes happen also, the secondaries alone survive, it sensitive seems possible that a flame with a short continuation of steady flame overtopping the region of tumult and confusion, could in this way be obtained. The hypothesis seems equally applicable to gauze flames, as nothing can prevent smoke-rings after smoke-rings from rolling up the contiguous sides of parallel jets nearly in contact with each other. Indeed, the difficulty of access of the outer air to the spaces between the jets must favour the production of vacua round the orifices, and accordingly the occurrence of air-whirls. This is perhaps the reason why wire-gauze flames begin to show sensitive properties at gas-pressures so much lower than those found necessary in the case of a single flame burning at a taper jet. The whole array of jets, it may be, in a wire-gauze flame behaves very nearly alike, and the flame as a body burns, whether noisily or silently, in the same manner, but with greatly increased susceptibility, as a single flame-jet from one of the gauze-meshes alone would appear to do. Whatever mechanical distinction may really exist between the mode of action of the common taper jet and the wire-gauze sensitive flames, it appears, therefore, rather to be one of a higher degree of susceptibility at low pressures, than of any more distantly distinct or special kind. Even the mode of operation of external sounds upon them is probably very similar in the two cases, for by rapid vibrations of the external air, such as a hiss or shrill whistle produces, the gas-jet leaving an orifice is shifted bodily to and fro over its edges, and nothing can more certainly produce partial vacua, and consequently air-whirls round its circumference, than sudden displacements of an air-jet laterally over the sides of its aperture, even if the tendency to develop them more or less periodically did not exist already in the critical or "sensitive" condition of the jet. Axial vibrations, also, or those impressed by outer disturbances on the gas current in the orifice in the direction of its flow, cannot be altogether without effect in producing vacua and air-whirls at its mouth; and among the multitudes of them thus occurring from the impressed action of external vibrations in all directions, a rhythmical selection is probably made depending on the form of the burner and the pressure of the gas. It is difficult to imagine how the partial air-vacuum or aspiration constantly existing round the nozzles of blast-apertures can bestow its energy when broken into discontinuity, rhythmical or otherwise, by a turbulent condition of the jet otherwise than by producing, in the peculiar eddy of its position, ring-shaped vortices encircling the blast; but it is evident that few jets and nozzles can be fashioned so smoothly in their inner and outer surfaces and edges that the ring vortices will often be complete; mere fragments of rings are scattered from their sides, which, having no stability, collapse with shocks and puffs that give the roaring and blustering character to the stream. With perfectly smoothed orifices there is probably every gradation according to the pressure of the gas, from full continuity of the partial vacuum or rarefaction round the jet, abating gradually and uniformly upwards to ultimate disappearance by friction with the surrounding air, through a condition of gentle undulations of this cone of rarefaction pursuing each other up the stream with slackening strength, and finally losing themselves also by friction as before, to the case of turbulence where the rings of rarefaction are quite intermittent, and separate ring-eddies more or less distinct from each other, of greater or less strength, and travelling up the stream with different speeds, take the place of the more gentle undulations. The distinction between ring-vortices and ring-shaped undulations is perhaps here too strongly and improperly overdrawn, as, besides the improbability that effects so exaggerated as perfect airwhirls are really ever attained in ordinary gas-jets, the properties of the undulations that correspond to and lead up to them in ordinary currents must evidently resemble theirs in all respects, so that the deeper and stronger interior undulations move up the jet more rapidly than open and weaker exterior ones on the surface; for it seems probable that both vortices and ring-waves of strongest rarefaction will generally occur nearest to the centre or axis, and those of weakest rarefaction furthest from it, or nearer to the slow-moving outer surface of the jet. The effect of the collision and destruction of a weaker by a stronger ring-wave, when they overtake each other, is the same as that of perfect circulating whirls; the balance of pressure in one part of the circular wave being broken by a shock, it collapses in every other part, and if both waves are destroyed, the further progress of the jet is intercepted at that point, and it scatters itself in a confused cloud at the point of concourse and disruption of the waves. The long-enduring smoke- or steam-rings often seen projected from the funnels of locomotive engines at starting, or when moving slowly and emitting separate puffs, illustrate apparently the mutual action of closely packed parallel jets like those of an ordinary gauze flame; for the impeded passage to the outer air offered by a number of such surrounding jets, just as by the funnel of the locomotive engine, favours the production of a strong vacuum round the jet-aperture or blast-pipe, and of a strong wave or steam-ring, the moment that the jet or blast takes a side-swing or a sudden leap upwards that calls the action of the partial vacuum into play. A. S. HERSCHEL (To be continued.) A New and Simple Method for making Carbon Cells and Plates for Galvanic Batteries SOME time since a correspondent asked for an easy method to construct carbon plates. A paper of mine was read in Section A at Belfast on the subject, and as it describes a process by which any experimentalist can construct not only plates but cells of carbon, I have thought a condensed account of the process may be appropriate for your columns. With a syrup made of equal quantities of lump-sugar and water, mix wood-charcoal in powder with about a sixth part of a light powder sold by colourmen, called vegetable black. The mixture should hang thickly on any mould dipped into it, and yet be sufficiently fluid to form itself into a smooth surface. The vegetable black considerably helps in this respect. Moulds of the cells required are made of stiff paper, and secured by wax or shellac. A projection should be made on the top of the mould for a connecting piece. These moulds are dipped into the carbon syrup, so as to cover the outside only, and then allowed to dry. This dipping and drying is repeated until the cells are sufficiently thick. When well dried they are then buried in sand, and baked in an oven sufficiently hot to destroy the paper mould. When cleared from the sand and burnt paper the cells are soaked for some hours in dilute hydrochloric acid, and again well dried, then soaked in sugar syrup. dry they are then packed with sand in an iron box, gradually raised to a white heat and left to cool. Should some of the cells be cracked, they need not be rejected, but covered with paper or plaster and dipped in melted paraffin. When Rods or plates of carbon can be rolled or pressed out of a similar composition, but made thicker. Carbon thus made will be found to have a good metallic ring and a brilliant fracture. Barnstaple, Oct. 26 W. SYMONS. Ingenuity in a Spider A SPIDER constructed its web in an angle of my garden, the sides of which were attached by long threads to shrubs at the height of nearly three feet from the gravel path beneath. Being much exposed to the wind, the equinoctial gales of this autumn destroyed the web several times. The ingenious spider now adopted the contrivance here represented. It secured a conical fragment of gravel with its larger end upwards, by two cords, one attached to each of its opposite sides, to the apex of its wedge-shaped web, and left it suspended as a moveable weight to be opposed to the effect of such gusts Note on the Rhynchosaurus Articeps, Owen REFERRING lately to Prof. Owen's description of the Rhynchosaurus ("Paleontology," p. 264), first discovered by myself in 1838-39, in the New Red Sandstone of Grinshill, near Shrewsbury, I remarked that in speaking of the ichnolites supposed to belong to this animal he says there is an "impression corresponding with the hinder part of the foot, which reminds one of a hind toe pointing backwards, and which, like the hind toe of some birds, only touched the ground.' In this account nothing is said of any claw being attached to this hind toe, nor have I met with any description of a claw in other authors. I have therefore thought it worth while to mention that I possess a specimen from Grinshill that shows distinctly the impression of a straight claw pointing backwards. There is also, on the same slab, the impression of another smaller foot of only three toes with strong straight claws, which has behind it a slight impression corresponding with the hind toe of the larger footprints. It is a curious fact that the claws of the larger impression, though larger than those of the smaller footprint, are so much recurved as not to project much beyond the ends of the toes, while on another slab from Storeton there are reliefs with both straight and recurved claws, the latter giving the idea of a foot like that of the Great Anteater. In these Storeton ichnolites the hind toe exhibits no claw, nor am I sure whether certain rounded elevations represent the smaller footprint in the Grinshill specimen. Upon another slab of Storeton stone I have a mark resembling the tail-mark on the slab presented by Mr. Strickland to the Warwickshire Museum, but unfortunately the footmarks connected with it are too indistinct to decide its origin. In a third slab from Storeton, besides several impressions with straight claws, there is one three inches long, the second toe of which has a straight clawg in. in length. I have also Cheirotherium footprints with long straight claws from the same quarries. I have put these few remarks together to fulfil the wish of Prof. Owen "to obtain the means of determining the precise modifications of the locomotive extremities of the Rhynchosaurus.' Perhaps by this time this object may have been attained, for at the Congrès des Savans at Paris in 1868 the discovery of two almost perfect skeletons was announced, and drawings of them were exhibited by a professor from Lyons. T. OGIER WARD [So far as the photographs can be deciphered, they seem to bear out the writer's statements.-ED.] THE ALPINE CLUB MAP OF SWITZERLAND* N NATURE, vol. vi. p. 203, we adverted to the nonexistence of a map of the Alps on a scale sufficiently large for general purposes, and briefly referred to the map which was then being produced under the direction of a committee of the English Alpine Club with the view of supplying the want. This map, though not yet finished, has been recently published. Three sheets are completely finished, but the fourth is still in outline, and will be exchanged for perfect copies when the hill-shading is added. We believe this to be, so far as it extends, the most bably no map of its size has ever been produced in this exact map of the Alps which has yet appeared, and procountry with more beautiful workmanship or with greater *The Alpine Club Map of Switzerland with parts of the neighbouring countries. Edited by R. C. Nichols, F.S.A., F.R.G,S., under the superintendence of a Committee of the Alpine Club. In four sheets. Scale rooms. (Stanford, 1874 ) elaboration of detail. We could have wished, indeed, that details had been inserted somewhat less profusely. It can never be possible in maps of the scale of this one (about one-quarter of an inch to a mile) to render, with a sufficient degree of clearness, all the minutia which are inserted in the great Government Surveys of civilised countries; nor can it ever have been supposed that this map would do away with the necessity of smaller maps of separate districts on a larger scale. Yet we find, in the map under review, in innumerable places, a mass of details which would have been amply sufficient had it been four times its dimensions, and a consequent want of clearness which is not a little perplexing. In some places, even the fantastic passes made in late years by the followers of the high art of mountaineering have been inserted, whilst in others (in the chain of Mont Blanc, for example) they have been almost entirely omitted, simply from want of space. Thus it appears, to those who are not informed, that in some places there are a great number of such passes, and in others scarcely any, when the reverse is perhaps the case. We should have advocated, both for the sake of consistency and of clearness, the omission of all passes except those of distinct utility. In point of clearness it must be admitted that the English Alpine Club Map is scarcely equal to the reduction of the Carte Dufour which was published last year in Switzerland, and this is not surprising. The authorities at Bern had to produce a simple reduction of the twenty-five sheet map of Switzerland, which was intended to be useful for general purposes, and to be issued at a low price so that it might be within the reach of everyone, and in this they have succeeded admirably. They had at their command most of the members of the staff who had been employed upon the survey, and thus had little or no difficulty in determining what to omit. This was a great advantage; for it must be obvious to all that, in reducing a map to a much smaller scale, it is more easy to determine what should be inserted than it is to know what should be left out. This simple fact, no doubt, accounts to some extent for the over-elaboration of the Alpine Club Map to which we just now referred. Its projectors also adopted the Carte Dufour as the basis of their map so far as Switzerland was concerned, but they had not the command of the very exact and minute topographical information which was possessed at Bern. It The reduced Swiss map, like the Carte Dufour, is a map of Switzerland, and for the most part stops abruptly at the frontier. The English map, however, is a map of Switzerland with parts of the neighbouring countries. extends everywhere sixteen miles more to the south than the most southern point of the Swiss boundaries, and in some places the country which it embraces (which is not included in the Swiss map) is as much as sixty-five to seventy miles from north to south. In the north and in the west the limits of the two maps are nearly the same, but in the east the English one includes the Orteler and several other important groups of mountains, which are not given in the Swiss one. The superficial area of the Alpine portion of the English map is altogether about one-half greater than that of the other, and the chief value of the map will be found to be in the part of it that represents this land beyond, but bordering the Swiss frontiers. It was a comparatively easy task, notwithstanding the complicated and exceedingly elaborate nature of the engraving, to render Switzerland after the Carte Dufour. The chief difficulty in the production of the map has lain in obtaining the material necessary for its completion towards the south. When it was commenced-now nearly ten years ago there was no map, even respectably accurate, of the chain of Mont Blanc in existence; and thence, right away to the furthest land in the east which is *Karte der Schweiz, in 4 blättern, reduciert unter der Direction des Herrn General G. H. Dufour, Maasstab, oooo. (Bern, 1873.) included, scarcely a square league could be adopted with confidence from any published survey. Hence it was necessary not only to examine every individual mountain and valley, but absolutely to re-survey several large districts. The chain of Mont Blanc, as it appears in the Alpine Club Map, is mainly taken from the special survey of Mr. Adams Reilly;* and so, too, is the whole of the southern side of Monte Rosa, as well as the large district bounded on the east by the Val d'Ayas, on the south by the valley of Aosta, and on the west by the valley of Valpelline.† This last-named district alone includes more than 150 square miles. The Graian Alps were in a state of hopeless confusion when Mr. R. C. Nichols took them in hand, and anyone who compares the map under notice with the best which were published previously will see what radical changes and corrections have been effected. Altogether, there is in the Alpine Club Map not less than a thousand square miles which have been entirely remodelled, and, for the most part, re-surveyed; this, moreover, being some of the most rugged and difficult country in Europe, containing numerous peaks from 12,000 ft. to 13,000 ft. elevation. Those who have been concerned in the production of the Alpine Club Map of Switzerland have a right to be proud of their work. We have tested it in the Alps, and it has stood the scrutiny extremely well. We cordially hope, though scarcely expect, that it will prove remunerative to its publisher, and that he will be induced to complete it by adding sheets to the east and to the west, so that at length there may be at least one map of the grandest and most picturesque chain of mountains in the world. In conclusion, a word is due to the engravers. The work was commenced by the late Dr. Keith Johnston, but the greater and the most difficult portions have been executed by Mr. John Addison. We have rarely seen better hill-engraving; and the wonder is, not that the appearance of the map has been delayed so long, but that a work of such magnitude and extraordinary minuteness should have been completed so soon. E. W REPORT OF PROF. PARKER'S HUNTERIAN LECTURES "ON THE STRUCTURE AND DEVELOPMENT OF THE VERTEBRATE SKULL" VIII.--Skull of the Common Fowl (Gallus domesticus). 'HE skull of birds is remarkable for the great amount THE of anchylosis which takes place between its various constituents long before the period of adult life. So complete is this union, that the determination of the separate bones in a full-grown bird is a perfectly hopeless task, without first studying their relation at a period when they retain their original distinctness. It will therefore be convenient to describe the fowl's skull, in the first instance, at the period of hatching, when the chief ossific centres are still separate, although most of the distinctive characters of the adult are already assumed. In this stage the foramen magnum is surrounded by the four perfectly distinct elements of the occipital segment, between which extensive tracts of cartilage still exist. The basi-occipital is comparatively small, and forms almost exclusively the rounded condyle (Fig. 27 O.C); the ex-occipital and supra-occipital are large and expanded, and into the latter extends the anterior semicircular canal (Fig. 26, a.s.c.), so largely developed in inner side of the cranial cavity, but outside is completely birds. The prootic (Fig. 26, Pr.O) is well seen on the hidden by the great development of the squamosal, which side wall of the skull. Two other auditory bones have takes a very considerable share in the formation of the *This has also been published separately on a scale of 80000 FIG. 25.-Skull of Fowl at the period of hatching (side view). p.p, pars plana supporting it, being, in fact, firmly anchylosed with the latter. A careful study of the earlier stages of development shows that only the upper part of this bone is really homologous with the basi-sphenoid, the lower part being the representative of the hinder part of the parasphenoid. The basi-temporal (Figs. 26 and 27, B.T), as this large membrane bone is called, is firmly anchylosed with the basi-sphenoid, the greater part of the inferior surface of which it completely covers, but is at this period still partially distinct from the representative of the anterior part of the parasphenoid (Figs. 26 and 27, Pa.S), the "basi-sphenoidal rostrum so characteristic of birds, which is, however, united with the basi-sphenoid. In front of the depressed basi-sphenoidal region the basis cranii becomes much compressed from side to side, forming a large cartilaginous interorbital septum, the representative of the prepituitary part of the basi-sphenoid and the presphenoid behind, and of the mesethmoid in front. The walls and roof of the brain-case are completed by the squamosals, alisphenoids, parietals, and frontals; the latter also affording support to the fore part of the base of the brain by means of their extensive in-turned orbital processes. The orbito-sphenoids are altogether absent at In front of this the cartilage is continued almost to the end of the beak as the septum nasi (Fig 26, s. n), or wall between the nasal sacs, the upper margin of which is produced outward into a wing-like expansion, the alinasal cartilage (Fig. 25, Aln) pierced by the external opening of the nostrils (A. N). A further continuation of the same median cartilages is seen in the slender pre-nasal or basitrabecular (Fig. 27, B. Tr). Within the nasal cavity are three pairs of cartilaginous folds, the alinasal turbinals represented by valvular processes of the ala nasi in some mammals, and the upper and lower turbinals, homologues of the structures bearing the same name in the higher class. The sole representative of the middle turbinal is the flat hinder wall of the ethmoid looking into the orbit, and known as the pars plana (Fig. 25, p. p). There is one more point of importance to be noted with regard to the interorbital septum, namely, the craniofacial notch (Fig. 26, c.f.n), a natural separation between the epi- and cerato-trabecular elements, and of great functional importance in the bird, where the beak is moveable upon a sort of hinge formed by the premaxillæ just above this point. The membrane bones of the face are yet to be considered. The premaxillæ are large bones partly fused FIG. 27. The same from beneath. Mx. Pa, maxillo-palatine process. together in the third line, and provided with well-developed nasal, palatine, and maxillary processes. On either side of the former of these backward projections are situated the nasals, processes from which come downwards and forwards to bound the alinasal cartilage posteriorly. The lacrymal is a largeish bone lying in the upper part of the front wall of the orbit, articulating with the nasal, and directed outwards and backwards. The bones of the upper jaw, or palato-maxillary apparatus, consist of two sub-parallel series, each of which articulates in front with the premaxilla, and behind with the quadrate; in the outer series are contained the maxilla, jugal, and quadrato-jugal, in the inner the palatine and pterygoid. All the bones in the former category are extremely slender-almost filiform, in fact; the palatines and pterygoids, on the contrary, attain a high degree of development, but neither they nor the maxilla develop palatine plates, the only rudiment of those structures being in the maxillo-palatine processes (Mx.Pa), flat plates of bone proceeding inwards from the maxillæ beneath the palatines to meet the small, single vomer. The palate of the fowl is thus formed on the simplest schizognathous type. The quadrate is a stout bone, having three well-defined processes, one forming the articular surface for the mandible; a second, answering to the otic process of the primitive suspensorium, articulates with the squamosal; and the third, or orbital process, projecting forwards and upwards, is the pedicle or true apex of the mandibular arch. The otic process, besides articulating with the squamosal, bears a small facet for the prootic; this, in many birds, is developed into a distinct secondary head. Immediately behind the quadrate is seen the large tympanic cavity; this is banded above by the supra-occipital and squamoid, below by the basi-temporal, behind by the ex-occipital, and in front by the basi-sphenoid; it sends into the latter a diverticulum, the anterior tympanic recess, and a second or posterior recess into the supraoccipital, through the diplöe of which it is continuous, as in the crocodile, with the tympanum of the opposite side. The fowl resembles the ostrich, and differs from most other birds in being wholly devoid of a tympanic bone. The lower jaw consists of the same elements as already described in the snake, except that the coronary is absent in the fowl, though present in most birds; in this stage the five bones (articular, angular, supra-angular, dentary, and splenial) are perfectly distinct, and Meckel's cartilage yet remains of considerable size. The upper part of the hyoid arch is separated, as in the snake and frog, to form with the stapes à columella auris. From the oval, irregular, plug-like stapes proceeds a slender rod of bone terminated by a triradiate cartilage, of which the slender antero-inferior bar is the infrastapedial, the broad somewhat expanded central segment the extra-stapedial, and the postero-superior bar the supra-stapedial. The latter is connected by an oblique bar with the extra-stapedial. The stylo-hyal is represented by the free end of the infra-stapedial. The tongue-bone consists of a body made up of glossohyal (formed by the union of the lesser cornua), basi-hyal, and basi-branchial (uro-hyal) arranged in a linear series; and of two pairs of cornua, the anterior or cerato-hyals, very small, and forming more lateral projections to the body, and the posterior or epi- and cerato-branchials (thyro-hyals), long and elastic, and embracing the occipital. The development of the fowl's skull has been worked out as far back as the fourth day; but even at that early period, when chondrification is only just beginning to set in, it is impossible to demonstrate with certainty the distinctness of many regions which are perfectly separate at corresponding stages in the lower types. At the period mentioned, the indifferent tissue of which the trabeculæ are formed is perfectly continuous with that of the investing mass, and this again with that of the auditory capsules. When, however, the process of conversion into cartilage is complete, the apices of the trabeculæ become perfectly distinct from the investing mass, and form a pair of backward-turned horns (often called the lingulæ sphenoidales) on either side of the pituitary space. The ear capsules, on the contrary, remain as undistinguishable from the para-chordal region after chondrification as before, and only acquire distinctness by ossification. This rapid process of fusion which takes place equally between the masses of indifferent tissue constituting the primordial skull, in the subsequently formed tracts of cartilage, and in the various ossifications of a still later period, renders the study of the bird's skull one of the most difficult problems of craniology. The manner in which the hyoid arch is developed has been worked out more exactly in the house-martin than in the chick, in which, however, the process is essentially similar. At a very early period the upper end of the arch grafts itself on to the auditory capsule, and at the same time becomes split up into three portions. The proximal of these constitutes the columella, a plug of the auditory capsule being before long cut out around its attached end to form the stapes. The middle is the stylo-hyal; it is at first connected to the columella by a tract of tissue, but afterwards fuses with the infra-stapedial element of the latter. The distal portion never becomes chondrified in its upper portion, resembling in this respect the corresponding structure in man (the stylo-hyoid ligament), but below forms the lesser cornu of the hyoid bone, or cerato-hyal. The mode of formation of the complex basi-sphenoidal region is, perhaps, the most important point which yet remains for consideration. No endogenous ossification takes place in the cartilage of this part of the basis cranii, but a pair of symmetrical ossific centres make their appearance in the thick web of perichondrium which underlies it, a third (median) centre appearing at the same time in front of the other two in the fibrous tissue below the ethmoidal cartilage. These ossifications together represent the dagger-shaped parasphenoid of the frog; the anterior is commonly known as the basisphenoidal rostrum; the posterior pair, coalescing, form the basi-temporal. Before they unite, however, ossification extends from them into the overlying cartilage, and thus the true basi-sphenoid is formed in a manner perfectly unique among vertebrata. THE NEW VINE-DISEASE IN THE SOUTHEAST OF FRANCE * II. HAVING thus far studied the spread of the new vinedisease and the extent of the ravages committed by the Phylloxera, it is time to turn our attention to the insect itself, and to state the results of scientific observation of the manner in which it attacks the vine rootlets, and the various circumstances and conditions which either favour or retard the development of the disease. The Phylloxera is a very minute insect, measuring, when fully grown, not more than 1-33rd of an inch in length. Its most striking feature is its proboscis, which lies in a sort of groove on the under-side of the insect, and with which it pierces the roots on which it feeds. This proboscis is very slender, and appears to be formed of three tongues, a greater one in the middle, and two more slender and shorter, on the two sides of it; it resembles a brown thread bending round and inserting itself in the tissue. The base of the proboscis is a sort of The Phylloxera. flat and sharp-pointed blade, composed of brown parts which prolong themselves into the tongues. The animal raises this blade a little in applying its proboscis to its food. The length of the sucker is equal to about half that of the body of the Phylloxera, which does not bury more than half of it in the bark of the roots. By this sucker the insect fixes itself to the spot which it has chosen, so that it can be made to turn upon it as on a pivot. In colour the Phylloxera, during the summer at least, is yellow, but in the late autumn it turns to a copper-brown tint, which lasts through the winter. The active life of the Phylloxera lasts from the beginning of April till the latter half of October. The insect hibernates through the other months, though previous to the commencement of hibernation the females who have laid eggs during the *Continued from vol. x. p 506. |