shall get the result stated. The curve obtained in this way is in reality identical with the other curves. By these four methods then we arrive at the conclusion that the last colour to be extinguished is the sensation which when strong gives the sensation of violet, but which when feeble gives a blue-grey sensation.

One final experiment I may show you. It has been remarked that moonlight passing through painted glass windows is colourless on the grey stone floor of a cathedral or church.

We can imitate the painted glass and moonlight. Here is a diaper pattern of different coloured glasses, and by means of the electric light lantern we throw its coloured pattern on the screen. The strength of moonlight being known, we can reduce the intensity of the light of the lamp till it is of the same value. When this is done it will be seen that the pattern remains, but is now colourless, showing that the recorded observations are correct, and I think you are now in a position to account for the disappearance of the colour.

I have now carried you through a series of experiments which are difficult to carry out perfectly before an audience, but at any rate I think you will have seen enough to show you that the first sensation of light is what answers to the violet sensation when it is strong enough to give the sensation of colour. The other sensations seem to be engrafted on this one sensation, but in what manner it is somewhat difficult to imagine. Whether the primitive sensation of light was this and the others evolved, of course we cannot know. It appears probable that even in insect life this violet sensation is predominant, or at all events existent. Insects whose food is to be found in flowers seek it in the gloaming, when they are comparatively safe from attack. Prof. Huxley states that the greater number of wild flowers are certainly not red, but more or less of a blue colour. This means that the insect eye has to distinguish these flowers at dusk from the surrounding leaves, which are then of a dismal grey; a blue flower would be visible to us whilst a red flower would be as black as night. That the insects single out these flowers seems to show that they participate in the same order of visual sensations. I venture to think, without adopting it in its entirety, that these results at all events give an additional probability as to the general correctness of the Young-Helmholtz theory of colour vision. Where the seat of colour sensation may be is not the point, it is only the question as to what the colour sensations make us feel which the physicist has to deal with. The simpler the theory, the more likely is it to be the true one, and certainly the Young-Helmholtz theory has the advantage over others of simplicity.

FR

"THE EPIGLOTTIS.”1

ROM an anthropotomical point of view the epiglottis had for a long time been generally looked upon as a kind of sentinel for the protection of the upper airpassages, when Rückert's comparative anatomical observations showed that the human epiglottis greatly differed from that of mammals, in so far as its relations to the soft palate were entirely altered, and that its physiological conditions pari passu had undergone important modifications. The new points of view thus obtained induced Gegenbaur to study the comparative anatomy of the epiglottis and its relations to the larynx, and the present volume is the outcome of his investigations.

The inquiry being undertaken from a morphological point of view the author begins with a study of the different forms of the epiglottis or epiglottoid structures in low classes of animal life. He next discusses the mammalian epiglottis and its relations to the soft palate. The con

1"Die Epiglottis," Vergleichend anatomische Studie, by Carl Gegenbaur, with two plates, &c. (Leipzig: Wilh. Engelmann, 1892.)

clusions here arrived at, and which concern the act of deglutition in the lower classes of mammals, lead to a consideration of other organs of the oral cavity, and to an attempt at establishing a connection between these and the apparatus consisting of the epiglottis and soft palate. This in turn induces a minute investigation of the structure of the epiglottis, and of its relationship to the framework of the larynx and the general structure of the respiratory organs in the lowest forms of animal life. In the last chapter the author summarizes the results obtained by his comparative studies and throws out such suggestions concerning the origin, development, and function of the epiglottis as would seem justified by his researches.

Brief as this survey of the course of Gegenbaur's essay necessarily has been, it will be sufficient to show that it is quite impossible to give in the space of a short review a detailed analysis of its contents. Conclusions derived from the synthetic conception of an enormous number of single observations, which extend over a large part of the entire animal kingdom, can only be properly appreciated by a study of the original, and this may be warmly recommended.

The final and most important conclusion arrived at by the author may be briefly summarized as follows:

Whilst as high up in the scale as in the sauropsida. parts of two branchial arches only contribute towards forming the primary hyoid, three more arches are added in the mammals. Two of these growing together form the transition into the thyroid, which becomes intimately connected with the larynx.

The mammalian larynx, however, has received a further addition, viz. the epiglottis, the cartilage of which can only be looked upon as the further development of the fourth branchial arch, which in fishes still serves its primitive function, and in the amphibia appears in a rudimentary form. The exact manner in which this rudiment passes over into the supporting organ of the epiglottis in mammals is, on the whole, still obscure. So much, however, is certain, that the cartilage of the epiglottis is not a product of mucous membrane, but a genuine part of the skeleton, and that it communicates its supporting function to the whole of the epiglottis, which serves as well the purpose of keeping the air-passages open as of protecting the vestibule of the larynx.

From this final conclusion it will be seen that, according to Gegenbaur, the role of the epiglottis in its highest development is purely a respiratory and protective one.

Pathological observation in man does not admit of these functions of the part being looked upon in any way as indispensable for the existence of the individual. Total loss of the epiglottis has often been observed in various diseases, without the patients either suffering from dyspnœa or from increased liability to the entrance of foreign bodies into the lower air-passages, the constrictor vestbuli laryngis (Luschka) in such cases vicariously taking its function. The supposed phonatory role of the epiglottis, upon which much stress is laid by some eminent singing masters (e.g. Stockhausen), inasmuch as they maintain that it influences, according to its more erect or more horizontal position, the "timbre" of the singing voice, is not even mentioned in Gegenbaur's essay. Thes many points connected with this subject still demand elucidation. Still it is impossible to withhold the expres sion of admiration and of gratitude to the author of the present work for his patient and extensive researches in a very obscure field of comparative anatomy.

NOTES.

On Saturday the British Eclipse Expedition to West Africa arrived safely at Bathurst. The Alecto was there, ready convey the party up the Salum River to the selected site.

ON Tuesday next, April 11, Mr. J. Macdonell will begin at the Royal Institution a course of three lectures on symbolism in ceremonies, customs, and art; on Thursday, April 13, Prof. Dewar will begin a course of five lectures on the atmosphere; and on Saturday, April 15, Mr. James Swinburne will begin a course of three lectures on some applications of electricity to chemistry. The Friday evening meetings will be resumed on April 14, when Sir William H. Flower will deliver a discourse on seals.

THE Academy of Sciences in Turin announces that the ninth Bressa prize of 10,416 francs, for which all men of science and inventors of all nations are free to compete, is now offered (from January 1, 1891, to December 31, 1894). The prize will be given to whoever, in the judgment of the Academy, shall have, within the period indicated, made the most important and useful discovery, or shall have published the most profound work in the domain of the physical and experimental sciences, natural history, pure and applied mathematics, chemistry, physiology and pathology, geology, history, geography, and statistics. Any one wishing to compete must send his printed work (manuscripts are not accepted) to the President of the Academy. Unsuccessful works are returned, if it be desired.

AT the meeting of the Chemical Section of the Franklin Institute, on February 21, a resolution was passed to the effect that the members had heard with deep regret of the death of their distinguished fellow-member, Dr. F. A. Genth, whose services as an investigator had "added lustre to American science.” A committee was appointed to prepare a suitable memoir of Dr. Genth for publication in the proceedings of the Section. ARRANGEMENTS have been made for another series of summer excursions by the London Geological Field Class. The object of these excursions, which are planned by Prof. H. G. Seeley, F. R.S., is the study of the physical geography and geology of the Thames Basin. The first excursion will take place on April 29, when the students will go from Edenbridge to Westerham by Toys Hill. Each excursion will be under Prof. Seeley's personal direction.

A SCHEME for the organisation of the proposed University for London was adopted at a general meeting of the Association for Promoting a Professorial University for London on March 23, and has been submitted to the University Commissioners. It is printed in the Times of April 3.

THE Scottish Technical Education Committee-appointed more than a year ago at a conference held in Edinburgh-has issued a report, from which it seems that Scotland has still a great deal to do before she can be said to possess a satisfactory system of technical instruction. At a recent meeting the Committee passed the following resolution:-"That, in the opinion of the meeting, it is desirable that the whole subject of higher and technical education should be dealt with in a comprehensive measure, and that the opportunity be not lost when the provision for secondary education is being inquired into in all parts of Scotland, to formulate a scheme for organising education beyond the elementary, and reducing in some degree the complications now existing, and the waste resulting from the various authorities that now have a connection with various parts of the educational system of Scotland, and that the chairman (Lord Elgin) be requested to take the necessary steps to bring the subject under the attention of the Government." At the same meeting the future action of the Committee was under consideration. It was felt that in present circumstances it would be very desirable to continue its existence if possible in some more definite shape, and a sub-committee was instructed to inquire under what conditions it might be brought into connection with the National Association for the promotion of secondary and technical education, and, if the sub-committee thought fit, to submit a form of constitution to the next meeting.

SHORTLY after eight o'clock on the morning of April 1 a severe earthquake shock was felt at Catania, and other places at the foot of Mount Etna. It was more especially pronounced at Nicolosi and Zaffarana-Etnea, where the population fled from their houses into the fields.

THE weather continued exceptionally fine over England dur. ing the whole of last week, and in Scotland and Ireland the weather was generally fair, although slight rain occurred at times in a few places. The first few days of the period were the warmest experienced as yet this season, and 70° was reached in parts of England. In the suburbs of London the shade thermometer registered 68° or upwards on four consecutive days, and this is the average maximum temperature in June; while on Saturday, April 1, the thermometer reached 71° in the outskirts of the metropolis. The general indications on Saturday were more favourable to a change than for some time past, but the unsettled appearance suddenly gave way to an anticyclone, which reached our islands from the Atlantic, and the conditions again became settled, although the maximum day temperatures during the last few days of the period were generally somewhat lower under the influence of a gentle easterly breeze. The mean temperature for March was several degrees in excess of the average over the whole kingdom, and at Greenwich the excess amounted to 5°; while the mean of all the maximum day readings, which was 57°, was higher than in any previous March during the last half century. The total rainfall for March was also small over the whole country, and at Greenwich the aggregate amount was only 0.38 inches, which is the smallest fall in March since 1854. The Weekly Weather Report for the week ending April 1 shows that the duration of sunshine was 85 per cent. in the Channel Islands, 76 per cent. in the south of England, and 72 per cent. in the east of England.

WE recently referred to the unsatisfactory condition of practical meteorology in Spain. The Royal Observatory at Madrid had for many years published results of observations taken at various stations in the peninsula, which furnish valuable materials for climatology; but daily telegraphic reports such as are issued in most other countries were necessary to complete the general synoptic view of weather conditions. We are glad to be able to report that this want has now been supplied. The first daily weather bulletin was recently issued, containing on one side a map showing isobars, wind direction and force, &c. ; and on the other the actual telegraphic observations at a number of stations distributed over Spain and south-western Europe. The bulletin is published by the Central Meteorological Institute, which was established some little time since under the direction of Prof. A. Arcimis, to whose persistent efforts we are chiefly indebted for this new contribution to our knowledge of current weather.

THE Meteorological Institutes of Hamburg and Copenhagen have issued their synoptic daily weather charts of the North Atlantic Ocean for the year ending November 1888. These charts contain the best materials for studying the various tracks and positions of the high and low pressure systems over the Atlantic; it is at once seen from them that in different parts of the ocean the storms take different routes, some follow a direct easterly track, others a more northerly course, while some form and others die out in mid-ocean. The great difficulty in storm prediction at present is to determine the routes that storms will take; a serious study of the conditions shown on such charts may eventually lead to the desired end, by enabling us to establish characteristic types of weather which accompany various depressions.

MR. W. H. GREENE and Mr. W. H. Wahl have elaborated a new process for the manufacture of manganese on the commercial scale. A paper by them on the subject was read before a recent meeting of the Chemical Section of the Franklin

will be indicated by a deflection of the galvanometer needle and a distortion of the lines of flow, usually designated by negative rotation." In the case of a paramagnetic body the rotation will be positive.

SEVERAL correspondents have written to us with regard to Mr. Hilderic Friend's letter on "Luminous Earthworms (NATURE, March 16, p. 463). Several of them record observations which seem to them to confirm his statements. Mr. R. I. Pocock, of the British Museum (Natural History), points out, however, that the property of phosphorescence exists in a highly-developed state in certain terricolous, nocturnal animals, which, although both luminous and vermiform, are certainly neither glowworms, nor yet earthworms. "The power of producing adhesive phosphorescent matter from pores opening upon the ventral surface of the body has," says Mr. Pocock, "been recorded from different quarters of the globe, in the case of several genera of centipedes of the family Geophilide; and since no special affinity is traceable between all the forms that are known to be sometimes luminous, it is highly probable that the presence of appropriate glands for the secretion of the matter in question is, or has been in the past, characteristic of the whole group. About a dozen species of Geophilide occur in the south of England. All may be described as worm-like, and some of them are known to be phosphorescent. Curiously enough, the specimens that have been not uncommonly brought to the Natural History Museum as phosphorescent phenomena are referable to a species, Linotania crassipes, which is the most earthworm-like of all, so far, at least, as colour is concerned. An example of this species was, I venture to suggest, the 'luminous earthworm' with the story of which Mr. Friend opens his account of the subject. This centipede is about one or two inches in length; and, although it is impossible quite to acquiesce in the statement that it is 'worm-like in all respects,' nevertheless I think it more than probable that a lady, finding one in the dusk of evening, when it could be but dimly seen, would summarily describe her idea of its appearance by some such expression as that used."

MR. J. E. HARTING, writing in the April number of the Zoologist, says that during a recent visit to Greece he lost no opportunity of interrogating the natives as to the birds and beasts to be met with, and was everywhere struck with the ignorance displayed on this subject, and the general indifference which prevailed respecting it. It was not until he reached the great plain of Larissa, where a plague of field voles has been for some time manifest, that he encountered those who could impart some information on at least one small indigenous mammal, namely, that which was causing such mischief and pecuniary loss to the resident land-owners. That it was a vole (Arvicola) of some sort was certain; but as to the precise species some difference of opinion had been expressed. Mr. Harting gives much very interesting information as to the animal's habits.

A PAPER on the foundations of the two river piers of the Tower Bridge, by Mr. G. E. W. Cruttwell, was read at the last meeting of the Institution of Civil Engineers before Easter. It was stated that the materials in the two piers, from foundation line up to a level of four feet above Trinity highwater (a height of 60 feet), consisted of 25, 220 cubic yards of cement concrete, 22,400 cubic yards of brick-work in cement, and 3340 cubic yards of Cornish granite; making a total of 50,960 cubic yards.

THE Agricultural Research Association for the north-eastern counties of Scotland has issued its report for 1892. A general outline of some of the past year's results is presented, and this

The

UNTIL comparatively recently bacteriologists have regarded the macroscopic appearances to which organisms give rise when grown on potatoes as affording valuable assistance in distinguishing between otherwise very similar microbes. One notable instance of this is the alleged different behaviour of the typhoid bacillus and the closely allied B. coli communis when inoculated respectively on to potatoes. But more recent research has shown that as a diagnostic agent the potato is extremely untrustworthy, and this has moreover been conclusively demonstrated in the case of just these two organisms. Further evidence on this subject has lately been brought forward by Krannhals, “Zur Kenntniss des Wachsthums der Komma bacillen auf Kartoffeln " (Centralblatt für Bakteriologie, vol. xiii. p. 33), and the results he has obtained in the case of the cholera organism are very instructive. When cholera declared itself at Riga last August, Krannhals, as Prosector and Bacteriologist at the city infirmary, was deputed to demonstrate officially to the city medical authorities that it really was cholera which had broken out. culture tests employed exhibited all the typical appearances associated with the cholera organism with the exception of its development on potatoes, upon which it obstinately refused to potatoes, slices were prepared and artificially rendered alkaline. grow. Suspecting that this might be due to the acidity of the On these the bacillus grew abundantly and moreover at from 16°-19° C., whereas it has hitherto been stated to be capable of only developing on this medium at from 30°-40° C. On the acid slices the same negative results were obtained as in all the previous experiments. In consequence of this discovery Krannhals conducted a large number of investigations on the behaviour of the cholera bacillus on acid and alkaline slices of potatoes respectively, and whereas he never failed to obtain vigorous growths on the latter even at the low temperature, he was only in very few instances (4 out of 136 experiments) able to induce its development on non-alkalised slices. But on testing those acid slices on which growths had appeared, it was found that they exhibited a distinct alkaline reaction. This alkalinity, moreover, had nothing to do with the growth of the bacillus, for sterile slices prepared in the same manner were tested both immediately on preparation and after they had been preserved some days, and the same astonishing result was obtained, i.e. that the slices of potato originally acid had during keeping become alkaline. Krannhals is led to suggest that in reality the cholera organism is incapable of growing on acid potatoes and that in those cases where it is stated to have developed on such, the medium unknown to the investigator must have, as in his experiments, changed from acid to alkaline. It is important that in future, therefore, the reaction of the potato should be noted both at the time of inoculation and later, when describing the growth of organisms on this medium.

NOTES from the Marine Biological Station, Plymouth :-Last week's captures include the rare Nudibranch Hero formosa, specimens of the spiny shrimp (Crangon spinosus), and of the starfishes Porania pulvillus and Henricia (Cribrella) sanguinolenta. In the floating fauna Plutei, large and small, have now quite taken the place of the Auricularia and Bipinnaria larvæ, which were so plentiful a few weeks ago. Arachnactis is still obtainable. The unmodified ephyræ of Aurelia are now very scarce: most of them are passing through various phases of their metamorphosis into the definitive medusa-form; and, instead of being plentiful everywhere, are now restricted to special localities.

THE additions to the Zoological Society's Gardens during the past week include a Bonnet Monkey (Macacus sinicus, 8) from India, presented by Mr. J. Pitcher; a Bengalese Cat (Felis bengalensis) from Manilla, Philippine Islands, presented by Mr. D. M. Forbes, F.Z.S.; three Peafowls (Pavo cristatus, &) from India, presented by Mr. T. Guy Paget; a Leadbeater's Cockatoo (Cacatua leadbeateri) from Australia, presented by Mrs. W. Everett Smith; five Black-headed Gulls (Larus ridi. bundus), a Common Gull (Larus canus) European, presented by

the Rev. E. M. Mitchell; three Rhomb-marked Snakes (Psammophylax rhombeatus), a Hoary Snake (Coronella cana) from South Africa, presented by Messrs. H. M. and C. Beddington; three Spring boks (Gazella euchore, ¿??) from South Africa, a Raccoon (Procyon lotor) from North America, a Green Monkey (Cercopithecus callitrichus) from West Africa, deposited; two silver-backed Foxes (Canis chama), a Cape Bucephalus (Bucephalus capensis) from South Africa, purchased; a Short Death Adder (Hoplocephalus curtus) from Australia, received in exchange; four Great Cyclodus (Cyclodus gigas) born in the Gardens.

COMET SWIFT (a 1892).—At the Boyden Station, Arequipa, Peru, during the visibility of this comet, all the photographic telescopes were turned towards it, with the result that a fine series of photographs were obtained. In the Bache 8-inch photographic doublet, fifty-six pictures (20 millimetres to the degree) were taken, sixteen of which "are of the first quality"; in the 2.5-inch photographic doublet (38 millimetres to the degree) twelve satisfactory plates were taken, while in the 13-inch refractor and 20-inch reflector several additional negatives were collected. An examination of the negatives, especially of those belonging to the first series, indicated two important facts, as Mr. A. E. Douglass (Astronomy and Astrophysics for March) informs us. (1) That the tail of the comet was composed of luminous masses receding from the head at a measurable rate, and (2) that the form of the tail depended largely on some varying force acting at the head. The former of these results was deduced from measurements of the distance of prominent points (8 points were here used) from the nucleus, and the acceleration he obtained amounted to 477,000 miles per day. In discussing the second fundamental results, he deals with the general characteristics of the tail and the special phenomena within half a degree of the head, separately. The tail he describes as "a bundle of slightly divergent straight streamers, branching from each other and joined to the head by one, two, or three well-marked lines." At the southern part of the tail the photographs showed the appearance of a curious twisting effect, while a number of faint streamers, in many cases not joined to the main part of the tail, were also visible. The curve

of the natural tangents of the position angles for the date on which they left the head, is, as plotted out by Mr. Douglass, quite irregular, and suggests "non-periodic outbursts from the head of the comet or variations in the repulsive force of the sun"; where the tail swings to one side there are "large jets in the opposite direction as if the whole resulted from some increase in activity in the head." He suggests that this activity may be connected with solar disturbances, just as magnetic

storms on the earth may be connected with certain classes of sunspots.

PARIS OBSERVATORY IN 1892.-From the annual report on the condition of the Paris Observatory during the year 1892, which was presented to the Council in January last by M. Tisserand, the Director, we gather the following brief notes

Commencing with a short reference to the late Director, l'Amiral Mouchez, and to the great loss both to the Observatory itself and to astronomical science in general, M. Tisserand informs us that, at the suggestion of M. O. Struve, the presidency of the Comité permanent de la Carte du Ciel has passed to the present Director of the Paris Observatory. This choice has been received very favourably, and been confirmet by all the members of the committee. Let us here tender oc congratulations to M. Tisserand, who, without doubt, will, ir his capacity as president, bring such a grand work as nearly 23 possible to perfection. In fact, he has commenced by increasing the personnel du Bureau de Mesures des Clichés at the Observatory, and constructing a new machine for the measures, while he hopes soon to publish a fascicule of the Bulletin de la Carte du Ciel, which will contain the method of reducing the measures, and of the definite computations of the positions of the stars. The large equatorial Coudé has this year been subjected to a qualities, and of the possibility of improving it still more. The minute study by M. Loewy from the point of view of its optical experiments have as yet been restricted to the mounting of the mirror, and it seems that important results may soon be forthcoming. The spectroscopical department, under the direction of M. Deslandres, has, as we are informed, quite assumed a definite form since its foundation in 1890; the work doce is tabulated under the three headings-sun, stars, and laboratory work. As we have previously referred in these columns most of the work here accomplished, such as, for instance, the researches of the velocities of stars in the line of sight (250 stars will here be included), photographs of protuberances, faculz new hydrogen radiations, &c., further notice will be unneces sary. With the Equatorial de la Tour de l'Ouest, the programme of observations has been the same as in previous years, measures of the positions of comets, nebulæ, and double stars having beet obtained. Among the observations here recorded as many 136 were made of Comet Swift (1892), 41 of Comet Denning (1892), while 250 nebule and 120 double stars have been measured. All the above were made by M. Bigourdan. M Faye also made 77 observations of comets. With the Cercl Méridien du Jardin under the special service of M. Loewy, the total number of observations amounted to 16.686; 453 obser vations were made of the sun, moon, and planets. M. Pa and Prosper Henry have obtaining been occupied in clichés of the international chart and of the catalogue; photo graphs have also been taken of the late nova in Auriga, Jupiter, and Comet Holmes. The Bureau des Mesures des Cliches d Catalogue, under the direction of Mdlle. Klumpke, has bee very busy. At this part of the report a brief description of the measuring machine is given, and in a paragraph on "reflexions sur le catalogue et la durée de son exécution," we are told that, if simply the 1200 or 1400 clichés which are demanded for the work in each of the eighteen observations are obtained peut espérer d'y atteindre en cinq ou six ans au plus." For measuring the clichés with one machine, and two persons t observe and write the results, 130 clichés could be done in a year, but it would take about 10 years to measure the cliche attributed to one observatory, with one machine and two per sons working incessantly. The report contains also all the meteorological work and that done with the minor instruments. concluding with the usual lists of personal publications, obser vatory publications, changes in the personnel, &c.

THE LARGE NEBULA NEAR & PERSEI (N. G. C. 1499).Dr. F. Scheiner, in Astronomische Nachrichten (No. 3157 describes briefly this great nebula near Persei, sever photographs of which he has been able to obtain. Durin November and December last, employing an objective 4-inch aperture, he took fine photographs, with exposure varying from 1 to 6 hours. The longest exposed plates showe that the size of this nebula has been considerably under-rated and that it comes nearly up to that of Orion and Andromes This nebula, it will be remembered, was discovered by Pr Barnard with a 6-inch objective, and the position which be gave, 3 h. 540 m. R.A. + 36° 1' Decl. (1855 0), referred >