is just possible that in these species the green is descended from, not yellow, but chestnut.

Quitting the greens, we now come to what is out and away the most satisfactory and interesting colour that I have studied-that is to say, red. Owing, however, to the very intimate relations of this colour to yellow, it is difficult to discuss them apart, and we will therefore take yellow and red together. Referring, now, first of all to the table of reds, what do we find as the general result? Omitting for the present (since they must be considered later) the last four species, we find that in practically every instance red is (rapidly or instantly) changed by acids to some kind of yellow or orange; or, to state it in terms of the views that I have been led to adopt, red is retrogressively modified into the yellow from which it was originally evolved.3 Here, however, the change stops; for, with the one striking and interesting exception of Delias (and perhaps one might add one or two of the pale pinks occurring among the Sphinges), the yellow thus produced is immovable. And since the species experimented upon include all varieties of red, and represent all the groups of Macro-Lepidoptera, one might apparently conclude that, although red is an exceedingly sensitive colour, yellow can never be affected. Yet, if the table of the normally yellow species be examined, it will be found that, in an immense number of these, the yellow is either partially or wholly dissolved by various reagents, leaving a pure white wing. Here, therefore, we find ourselves at once face to face with the problem of the character of the yellow pigment, and to a consideration of that we must turn before proceeding further with red.

It will be observed that in this table of yellows I have divided the species examined into four groups. Omitting for the present the small second group, we may distinguish three stages, represented by the three groups 1, 3, and 4. This division has been adopted in order to illustrate what seems to me the most feasible explanation-at least for the present-of the constitution and behaviour of this yellow pigment. In the first group the yellow is exceedingly soluble, and a colourless white wing is the result. In the next stage (the third group) the yellow is more or less affected-sometimes very little moved, sometimes finely dissolved. In the last group the yellow is wholly insoluble and entirely unaltered. Also be it noted that in group 1 pale light yellows predominate, while in the last group the yellow is chiefly orange. It is, further, clear from this that a complete classification of all the yellows would include in this fourth group all the yellows artificially produced by reacting on the reds. Now, the explanation which I have adopted in order to cover all these facts is as follows. It appears that the yellow pigment, when first evolved, is exceedingly sensitive and susceptible of evolution by various reagents; in this stage, too, it is probably of a comparatively pale or light yellow colour. In course of time the yellow pigment may in various instances become slightly altered in constitution (generally accompanied by a change to a deeper or more orange tint), and altered in the direction of greater stability; or rather, to confine ourselves to the literal facts, altered to the extent of becoming far less soluble. Of this intermediate stage we have examples in group 3. Finally, in group 4 we have examples of the last stage of evolution, when an—usually

I have not thought it worth while to refer here to the pseudo green of Euchloa cardaminus: vide Entomologist, May 1891.

It is unnecessary here to regard the less marked and less interesting alkaline reaction.

3 Some remarks on this subject will be found in the Entomologist, xxiii.

370-71.

4 It is, of course, to be understood that, like all rigid divisions, this is to some extent artificial. Evidently Nature knows nothing of three or four sharply circumscribed groups of yellow, but merely an indefinite series, of which the first members would fall into my first group, and the last into my fourth, and so on.

I speak, of course, in a phylogenetic sense.

It

deep-coloured--insoluble yellow has been evolved. appears to me, therefore, that usually red is evolved only after a long apprenticeship of yellow, and this is as much as to say that as a rule the yellow has become stable and insoluble before its evolution into red: this explains why red can be converted into yellow, but usually no further. On the other hand, the striking instances of Delias and one or two pink species show that occasionally the development of red has been so rapid that the yellow had not previously become stable.1 The very parallel examples of Cardaminus edusa and Lycæna phlæas and virgaurea should be compared with these.

Were

There is, however, still in my mind an open point as regards several of the yellow species in the last group; for it is not clear by any means that we may not have included here one or two physical yellows as well. We know that the yellows of the first three groups are entirely pigmental, for their solubility shows this; and we know that in the fourth group several species, such as Deiopeia bella, C. hera lutescens, A. villica, are pigmented, since their relations to red species which yield a similarly insoluble yellow proves this; but in the case of, for instance, T. pronuba (the "Yellow Underwing") and its miniature analogue Heliaca, we are totally in the dark; and it appears safer to me to withhold for the present any opinion as to whether these be physical or pigmental yellows. there any red underwing in the same genus as either of these, that would be sufficient to justify us, by analogy, in considering the yellow of these species pigmental, just as we do that of, e.g., Arctia villica; but failing such evidence, the experimental evidence is not decisive in either direction. There is, however, a most remarkable and exceptional set of phenomena connected with these yellows that I once thought might prove the criterion by which to distinguish between pigmental and possibly physical yellows in doubtful cases such as that of T. pronuba. Some time ago it was incidentally observed by Mr. Edwards that the wing of a species of Colias left in a damp cyanide bottle was turned red. This statement was brought under my notice by Mr. T. D. A. Cockerell, first of all in the columns of the Entomologist, and later in a private communication. I must frankly admit that for a long time I remained entirely incredulous of this alleged fact, since it was utterly opposed to all my own experience. I had observed nothing but retrogressive modifications of colour. whether by solution or simple change, and had found potassic cyanide (in solution) to rapidly dissolve the yellow of Colias, leaving a simple white wing: it was therefore very difficult to credit such a statement.

I will not trouble the readers of NATURE with any detailed account of my experiments in this direction, made with the purpose of verifying—or otherwise-the correctness of Mr. Edwards's statement; but will simply say that I finally succeeded (owing really to a lucky accident) in verifying this. A yellow wing of Colias placed on wet cyanide is turned red, in spite of the solvent action of the cyanide: such an effect could never be attained by using a cyanide solution, because all the yellow would be dissolved out of the wing in a very short time; it is therefore necessary to hit the happy medium between dry cyanide and solution: as it is, a good deal of the yellow always goes into solution, but sufficient is left in the wing to be reddened. I have not stopped, however, at Colias, but have examined a number of other yellow species, with the result that I find many yellows become changed by this method to a really brilliant red I See a full discussion in the Entomologist for January last.

It is, however, to be noted that in one case I found the yellow of 7. pronuba very faded; but I do not care to contend for a pigment on the strength of this alone.

3 An account of these will be found in the Entomologist for July 1891. I hope that I have made it sufficiently clear that I have no shadow of a claim to any credit in discovering this extraordinary phenomenon. Most certainly I should not have found it out in the course of my own experiments. or even afterwards but for Mr Cockerell's insistence on the accuracy of his

statement.

-which red seems indefinitely permanent if the wing be removed and dried. It will be seen that, in the table of yellows, several species are marked as showing the "cyanide effect"; whilst others are marked "no cyanide effect." The former are those in which I have succeeded in obtaining the reddening; the latter will not redden. Now, since the former are all known to be pigmental yellows, whilst one of the latter, viz. T. pronuba, is the doubtful case, it seemed probable that this cyanide reaction might take place always and only with pigments, and thus afford the desired criterion. But in extending my experiments this hope proved fallacious, for I found-as is noted in the table-that various pigment yellows gave no reaction: the typical case on which I relied was Č. hera lutescens: had this yellow, which is assuredly pigmental, although quite insoluble, been reddened, I should have felt justified in accepting the criterion. But not the slightest reaction took place with this species. I must not linger longer on this certainly fascinating subject: it is clearly one that requires thoroughly working out, and my investigations thereupon, are being carried on in several directions; but I may point out the great interest attaching to a reaction by which we can produce a coloric change practically identical (at least in its effects) with that which progressive evolution has produced in many species formerly yellow but now red.

Before, however, quitting yellow, there are one or two points yet that need explanation. In group 2 in the table, I have included two species showing a rich orange colour: this, though clearly marking a considerable progress in coloric evolution from the presumably primæval pale yellow, is yet exceedingly soluble: these instances, which, therefore, are very comparable with the red of Delias, are another proof that advance in depth and richness of colour is not necessarily always accompanied by decreasing solubility. I may add that I do not regard the orange of these two species as being in the direct line of evolution from yellow to red, but rather as a collateral or branch line also springing from yellow. It is specially interesting that in this circumstance, as also in so many others, there is an exact parallel among the

chestnuts.

And lastly, among the phenomena of yellow, we have to deal with the reaction of Argia galathea, already referred to; a reaction in which, contrary to all other experience, a white wing is changed to yellow by various reagents. It is very evident that, since I deny the existence of any pigment in white wings, and assert the yellow to have been developed in a previously unpigmented wing, and not by evolution from a white pigment, it is all-important for me to clear up this matter. My explanation, which has been given in some detail in the Entomologist (xxiii., pp. 341-43), is-to be as brief as possible the following. It is, of course, well known that the pigments of both animals and plants are decomposition products of the protoplasm, whether produced directly by decomposition of the protoplasmic molecule, or indirectly by union of two or more decomposition products. Now, I take it that in this species-A. galathea-the metabolic processes have not yet produced any pigment, but very nearly so; that there exists in the wing a very unstable mother-substance (itself a decomposition product, whether produced immediately from the protoplasmic molecule, or indirectly from a molecule of intermediate complexity); and that the action of any powerful reagent is to decompose this, forming the yellow pigment; which pigment, as soon as formed, commences to dissolve in the reagent, as so many normal yellows do.3

I have also obtained it with Loxura atymnus. It is very significant that I have in n case obtained jt among the Heterocera (moths), but only among the Rhopalocera. Cp. infra, cn chestnut.

It is very interesting that the orange of G. cleopatra first of all is changed to the ground yellow, and then dissolved.

3 I may point out that in the female of A. galathea there is already a cream tint in the wings.

This view, although at present necessarily somewhat hypothetical, appears to me to offer a satisfactory explanation of the apparently anomalous behaviour of galathea. F. H. PERRY COSTE. (To be continued.)

NOTES.

The

MR. ALFRED RUSSEL WALLACE AND MR. EDWARD WHYMPER are to receive the Royal Medals of the Royal Geographical Society at its annual meeting on May 23 next. annual dinner of the Society will be held on the evening of that day after the annual meeting. The annual conversazione will take place about the middle of June in the South Kensington Museum.

MR. CHARLES HOSE, Resident on the Baram River, in the Rajahship of Sarawak, has recently explored that river to its sources, and ascended Mount Dulit, one of the summits of the main range which traverses this part of Borneo, to a height of 5000 feet. His zoological collections, which have been forwarded to the British Museum, contain many fine novelties. Among the mammals, which were described by Mr. Oldfield Thomas at the last meeting of the Zoological Society, are representatives of a new Carnivore of the genus Hemigale, two new Insectivores of the genus Tupaia, and a new Squirrel. The birds, which are being worked out by Dr. Bowdler Sharpe for The Ibis, likewise contain several remarkable new forms, amongst which is a new species of the restricted Eurylamine genus Calyptomena, intermediate in size between C. viridis and the large C. whiteheadi of Mount Kina-balu. Mr. Hose is a nephew of Dr. G. F. Hose, the Bishop of Singapore and

Labuan.

AMONG the names attached to the recent protest of members of the corporation and teaching staff of University College, London, against the Gresham Charter, we notice the following representatives of science and Fellows of the Royal Society :Sir F. Abel, Prof. I. B. Balfour, Sir Henry Bessemer, H. S. Caxter, Sir J. N. Douglass, W. T. Thiselton-Dyer, Prof. W. H. Flower, Prof. E. Frankland, Dr. George Harley, R. B. Hayward, H. Hudleston, Prof. T. H. Huxley, Prof. E. Kay Lankester, Prof. Norman Lockyer, Prof. O. J. Lodge, Sir John Lubbock, Prof. D. Oliver, Prof. J. Prestwich, Prof. G. J. Romanes, Sir Henry Roscoe, Prof. Burdon Sanderson, J. Wilson Swan, Prof. Sylvester, E. B. Tylor, and Prof. W. F. R. Weldon. The protest contained equally influential names in the fields of literature, art, and politics; thus forming a document having no small weight in the final decision of the Government regard. ing this futile attempt to solve the problem of a Metropolitan University.

WE regret to have to record the death of Sir William Bowman, F.R.S., the eminent ophthalmic surgeon. He died of pneumonia at Joldwynds, his house near Dorking, on Tuesday last. He was born on July 20, 1816. In 1840 he was elected assistant surgeon at King's College Hospital, where he afterwards became full surgeon. He was also for a time assistant surgeon, and then full surgeon, at the Royal London Ophthalmic Hospital. He acted as the first president of the Ophthalmological Society of Great Britain, which he helped to found; and in 1884 he was created a baronet in recognition of his professional eminence. Sir William was a master of the various methods of ophthalmic surgery, and did much to improve them and to place them on a sound scientific basis. He held a leading place among those who made accessible to English students the knowledge obtained by the invention of the ophthalmoscope; and to him belongs the honour of having overcome the hostility

with which Von Graefe's operation of iridectomy for the cure of glaucoma was received by some authorities in this country. He also devoted much attention to the treatment of obstructions of the tear passages, and to improvements in the operation for cataract. His microscopic work, so early as 1840, was recognized as work of high value. He was elected a Fellow of the Royal Society in 1841, and received one of the Royal Medals in 1842. He was a member of many other scientific Societies both at home and abroad, and honorary degrees were conferred upon him by the Universities of Cambridge, Dublin, and Edinburgh.

DR. R. THORNE THORNE, F. R.S., will succeed Dr. George Buchanan, F.R.S., as medical adviser to the Local Government

Board.

PROF. LODGE has, with the approval of the Senate, appointed to the demonstratorship in electrotechnics at University College, Liverpool, Mr. Francis Gibson Baily, late Scholar of St. John's College, Cambridge. Mr. Baily took first-class honours in the Natural Science Tripos, and is now in the employ of Messrs. Siemens Bros. and Co

THE Revue Scientifique notes that at Kieff there is a chemist | who is nearly as old as the late M. Chevreul was at the time of his death. This is Prof. Ignace Vonberg, who was born at Vilna on January 17, 1791. He was one of the last Professors of Chemistry at the old University of his native place, and afterwards held, until 1866, a similar position at the University of Kieff. He is said to enjoy excellent health.

IT has been decided, according to Norwegian newspapers, that Dr. Nansen's North Pole Expedition shall start on January 1, 1893. He has selected as members of the Expedition a young officer in the Royal Norwegian Navy, Herr Sigurd Scott-Hansen, who will make the astronomical observations, an experienced Arctic navigator, Captain J. Ingebrigtsen, from Tromsö, and Herr Sverdrup, by whom Dr. Nansen was accompanied in his journey across Greenland.

EVERYONE who occasionally visits the Zoological Gardens was sorry to hear of the death of the giraffe. Since May 24, 1836, the Gardens have never until now been without one of these interesting animals. Dr. P. L. Sclater, writing to the Times on the subject, says that during the past fifty-five years there have been in the Gardens thirty giraffes, of which seventeen have been bred and reared there. A male born on April 22, 1846, lived in the Gardens nearly twenty-one years. These facts prove, as Dr. Sclater says, that this animal (one of the most extraordinary forms among recent mammals) is quite fitted for captivity, and is well worthy of the expense and trouble incurred in its keep. The closure of the Soudan by the Mahdists has prevented the importation of giraffes for some years, and for the only individual now in the market (an old female) a prohibitive price is asked. The Zoological Society hope that the need may be supplied by some of their friends and correspondents in Eastern or Southern Africa.

DR. B. W. RICHARDSON will deliver at the Royal Institution his Friday evening discourse on “The Physiology of Dreams" on April 29, in place of Dr. William Huggins, who will give his lecture on "The New Star in Auriga" on May 13.

PROF. W. G. OWENS writes to us from Bucknell University, Lewisburg, Pa., U.S., that on March 15, at 2 o'clock p.m., a series of halos and parhelia appeared and increased in brilliancy until 4 o'clock, after which they faded gradually till sunset. The circles, arcs, and spots around the sun were highly coloured, sometimes showing almost the entire spectrum.

THE Report of the Meteorological Council for the year ending March 31, 1891, has recently been issued. The follow

ing changes relating to organization were under consideration during the year: (1) the purchase of a new house near Cahirciveen, to which it is proposed to move the Observatory from the island of Valentia, the former place being more suitable for observations; (2) the registration of the Council as a corporate body, under section 23 of the Companies' Act, 1867; (3) examination of clerks, keeping as far as practicable to the system followed in the Civil Service. The practice followed by the Office with reference to observers at sea remains unchanged. The number of voyages for which logs have been returned during the year was 156; instruments have also been supplied to various islands in the Pacific, &c. In the weather forecasting branch, a comparison of the forecasts issued at 8.30 p.m. during the year with the weather actually experienced, shows that the total percentage of success was 82. The results were best, 88 per cent., for the south of England, and worst, 77 per cent., for the south of Ireland. The hay harvest forecasts were very successful; as much as 95 per cent. of success was attained in some parts. To add to the means of obtaining warnings of stormy weather at exposed fishery 'stations, the useful practice of lending trustworthy barometers, adopted by Admiral FitzRoy, has been continued; the number of stations now supplied is 180. The subject of cloud photography has continued to receive attention, and the system of observation and reduction has been improved, so that there is reason to expect that satisfactory determinations both of the heights and the velocities of the various clouds will be made. The Council have requested Mr. W. H. Dines to carry out a series of experiments at Oxshott for the purpose of comparing the action of various forms of anemometers, as well as experiments on the resistances of curved plates and vanes. The work is nearly finished, and the results will be published.

THE Deutsches meteorologisches Jahrbuch, Bavaria, 1891, Heft 3, contains twelve cloud pictures, reproduced from photographs supplied by Hildebrandsson, Riggenbach, and others. These photographs have been collected by Dr. Singer, of Munich, who submitted some of them to the International Meteorological Conference held there last autumn, where the importance of the artistic representation of clouds was discussed. The Cloud Atlas, published at Hamburg in 1890, was recognized by a large majority as the first satisfactory attempt to obtain uniformity in cloud nomenclature; but a Committee was framed to further consider the future production of pictures in a cheap form, according to the types approved by the Conference, and Dr. Singer was asked to join that Committee. The pictures now in question may be considered as his contribution to the subject. The forms are well defined; the names proposed differ materially from the classification by Luke Howard, hitherto generally in use, more attention being paid to the average heights of the various types. There are, however, still distinct variations of cloud frequently seen, which are not represented in Dr. Singer's collection, and his system of classification, notwithstanding its merits, bas defects which must, sooner or later, be dealt with.

THE Times of March 24 printed the following communication from a correspondent:-Under the direction of the Austrian Government an interesting series of deep-sea explorations has been conducted recently in the eastern parts of the Mediterranean, by a scientific party on board the Pola. At one point, about 50 nautical miles south-west from Cape Matapan, the Pola found a depth of 4400 metres (2406 fathoms), followed within a few miles further east by a depth of 4080 metres (2236 fathoms), which are the greatest depths recorded in the Mediterranean. They have received from the Austrian Hydrographical Board the name of Pola Deep. The great depression of the Mediterranean must thus be shifted considerably cast from its former central position on the maps. Another deep area was