densor or micro slide mounting materials.-William E. Daw, jun., West Winch, King's Lynn.

SEVERAL foreign books, mostly German, including one on natural history. Lists sent on application. Also a pair of ivory gilt opera glasses by Pillischer, in exchange for natural history books or offers. Unaccepted offers not answered.-F. H. Parrott, Walton House, Aylesbury.

WILL exchange books: Buckmaster's "Elementary Chemistry" and Jarmain's "Qualitative Analysis," also, the "A. B. C." water-testing apparatus (very interesting), for slides of well-mounted algæ, zoophytes, polycistina, diatoms, or bacteria.-H. W. Case, Oxford Street, Cothamn, Bristol.

DUPLICATE microscopic slides of various sorts, and Lepidoptera to exchange for other slides-algæ, and fossil woods or other rocks.-A. Wells, Dalmain Road, Forest Hill.

DUPLICATES of dried plants, L. C., 7th edit., Nos. 7, 9, xi, 26, 40, 41, 273, 2736, 274, 275, 305, 325, 350, 372, 374, 564, 568, 572, 574, 576, 577, 581, 587, 591, 594, 595, 813, 816, 821, 823, 831, 835, 838, 856, 858, 875, 914, 998, 999, 1007, 1008, 1039, 1040, 1261, 1264, 1265, 1276, 1277, 1280, 1282, 1285, 1294, 1295, 1297, 1305, 1314, 1325, 1326, 1327, 1330, 1333, &c.-H. Goss, Berrylands, Surbiton Hill, Surrey.

To American diatomists: American gatherings or deposits desired in exchange for pieces of the well-known "Cementstein" from Mors, Jutland. Send list in first instance.-H. Morland, Cranford, near Hounslow.

OFFERED, L. C., 7th edit., 48b, 49, 360, 384, 455, 1024, 1041, 1106, 1187, 1188, 1240, 1417, Carex java, minor, &c. Wanted, 363, 370, 404, 1050, and many others. Lists exchanged.Dr. A. Davidson, Sauquhar, N.B.

DAVUS, Artaxerxes, Dicteæ, fuliginosa, bidentata, interrogationis, and many other northern species, in fine condition and well set. Wanted, fresh-killed specimens of barn owl, kingfisher, and local specimens, &c.-J. Mundie, 22 Watson Street, Aberdeen, N. B.

DUPLICATES.-Bulbs: Narcissus bicolor, major, Macleai, orientalis, pseudo-narcissus fl. pl., poeticus, ornatus, Bulbocodium, triandrus, &c., Lilium Californicum, Chalcedonicum, eximium, Gladiolus Byzantinus, G., Colvillei alba, Cyclobothra pulchella, Allium Neapolitanum, Iris reticulata, Anemone fulgens, Hemerocallis flava, &c. Wanted in exchange, other choice bulbs, &c., British and foreign Lepidoptera, rare British and foreign shells, scientific (especially botanical) books; all offers invited and replied to.-J. T. R., Spring Cottage, Dee Banks, Chester.

LIVING specimens of Limnias ceratophylli offered in exchange for well-mounted slides, selected diatoms preferred.-G. A. Barker, 1 Northwold Road, Upper Clapton, E.

SCOTCH Alpine and sub-Alpine mosses and hepaticæ for south of England species, especially from chalk and limestone.William Smith, Addison Place, Arbroath, N.B.

WANTED, Roscoe and Schorlemmer's "Chemistry" and Dana's "Mineralogy," latest editions. Will exchange Beale's "How to Work with the Micro," and other good books.-F. C. King, 2 Clarendon Street, Preston, Lancashire.

"MINING JOURNAL," complete, clean, unbound, 8 vols., 1876 to 1883 inclusive; exchange for "Micrographical Dictionary" and Lyell's "Principles of Geology," or offers; books, &c., microscopical and geological preferred.-J. Barron, Wakefield." OFFERED, twenty-four packets of microscopic material in exchange for three good slides or other material.-W. Sim, Gourdas Fyvie, N.B.

ZOOPHYTES and Polyzoas in exchange for others.-J. Smith, jun., 63 Legh Street, Warrington.

WANTED, a copy of Johnson's "British Zoophytes;" state wants.-J. Smith, jun., 63 Legh Street, Warrington.

Wanted, good micro slides; skins and mounted specimens of mammals and birds, and other objects, offered in exchange.F. R. Rowley, 60 Lower Hastings Street, Southfields, Leicester. SUBSCRIBER'S edition of Cassell's "History of the United States," by Edmund Ollier, 3 vols., complete, unbound, profusely illustrated with wood engravings and 30 steel plates; exchange for Geikie's or other good "Geology."-H. P. Dodridge, 7 Wharton Street, W.C.

OFFERS requested for "Midland Naturalist," complete series, up to end of 1885.-F. G. S, 2 The Polygon, Clifton, Bristol. WANTED, binocular microscope with rotating stage in exchange for monocular. Full particulars to-J. B., Gillsburn, Kilmarnock, N.B.

MICROSCOPE by Steward, Strand; capital instrument, with in. objective, polariscope, condenser, and mahogany case, all in thorough condition; will exchange for another secondhand, large size, with latest improvements.-H. W. Case, Cotham, Bristol.

WHAT offers for "Hopkinson on the Indicator" and SCIENCEGossip for 1880 ?-Archibald W. Fry, Bridge House, Arundel. WANTED, British wild bees (fresh specimens only), must be correctly named. Good exchange given in micro slides.C. Collins, Bristol House, Harlesden, N.W.

SIDE-BLOWN eggs of willow wren, marsh tit, pied wagtail, yellow wagtail, ring dove, hooded crow, mallard duck, coot, Arctic tero, black-headed gull, guillemot, and others; wanted, other eggs in exchange.-A. Kelly, 5 Canal Lane, Aberdeen.

A GREAT number of duplicate Coleoptera and Lepidoptera, all well-set and in good condition, to exchange for birds' eggs

or skins, works on oology, or books of sport. Serd for lists toW. P. Ellis, Enfield Chase, Middlesex, N.

BRITISH and American birds' skins in exchange for magic lantern slides or offers.-James Ingleby, Eavestone, Ripon. FOSSILS from the shell bed in the millstone grit for fossils from the red crag or others.-James Ingleby, Eavestone, Ripon. FRESHLY-COLLECTED marine sponges, zoophytes, anemones, &c., offered in exchange for shells, eggs, or other natural history specimens. Offers requested.-C. Jefferys, Tenby.

HUMMING-BIRDS' skins, in good condition; what offers? SCIENCE-GOSSIP for 1884, in numbers, clean.-Joseph Anderson, jun., Acre Villa, Chichester, Sussex.

A GOOD exchange offered for following nests containing clutch of eggs, with data: pied flycatcher, nightingale, stonechat, marsh warbler, Dartford warbler, woodwarbler, great tit, rock pipit, woodlark, cirl bunting, hawfinch, goldfinch; also wanted, foreign species, nests with eggs.-W. K. Mann, Wellington Terrace, Clifton, Bristol.

WILL send three Hydra fusca in tube, or two young newts with external gills showing circulation of blood, in exchange for well-mounted slide, stained biological preferred. Mr. Swainson, Gilnow Park, Bolton.

EXCHANGE Helix visana, Helix obvoluta, Bulimus acutus, and var. bizona, Bulimus montanus, Clausilia laminata, var. albida; for Limnæa involuta, Succinia oblonga, Acme lineata.-J. Madison, 167 Bradford Street, Birmingham.

WILL give Cyclas ovalis, Paludina Listerii, for Alismadon margaritifera, Unio tumidus, Unio pictorum.-G. C., 68 Rutland Street, Hulme, Manchester.

WANTED, British or foreign land and freshwater shells. Can give in exchange, Cl. biplicata from Putney, P. fontinale, P. roseum, Pl. lineatus, Z. radiatulus, V. antivertigo, Balea perversa, Coch. tridens, &c.-F. G. Fenn, 20 Woodstock Road, Bedford Park, Chiswick, W.

DUPLICATES, Cataulus pyramidatus, Cataulus Skinneri, Helix Skinneri, Helix Waltoni, H. Gardneri, and many other rare shells from Ceylon. Wanted, rare fossils from Upper Miocene of France and Italy, or state offers.-J. E. Linter, Arragon Close, Twickenham.

BRITISH marine shells wanted in exchange for Kellia suborbicularis, Mya Binghami, and others.-G. O. Howell, M.C.S., 3 Ripon Villas, Ripon Road, Plumstead, S. E.

I SHALL be happy to send types of Suffumata and numerous other insects free to beginners in the study of entomology. Box and return postage to be sent.-W. Macmillan, Castle Cary, Somerset.

A BEGINNER Would be glad of a few duplicates of land, freshwater, and marine shells; alga, beetles, however common, would be thankfully received, postage paid and acknowledged. -Xema, 28 South Street, Carlisle.

FOR Small piece of "cementstein" from Mors, Jutland, (easy to clean and rich in diatoms), send stamp and address to -H. Morland, Cranford, near Hounslow.

BOOKS, ETC., RECEIVED.

"Our Insect Enemies," by Theodore Wood. (London: Soc. Prom. Christian Knowledge.)-" First Year of Scientific Knowledge," by Paul Bert. (London: Relfe Bros.) "British Cage Birds," Part I., and "The Book of the Goat," Part I. (London: L. Upcott Gill.)" American Monthly Microscopical Journal."-"Cosmos."-"Reports of the Botanical Exchange Club of the British Isles for 1883 and 1884."-" Proceedings of the Literary and Philosophical Society of Liverpool, 1883-4." (London: Longmans.)-Science."-" Journal of the New York Microscopical Society."-"The Canadian Entomologist." "The Amateur Photographer."-" Ben Brierley's Journal." -"The Rochdale Field Naturalists' Journal."-"Feuille des Jeunes Naturalistes."-"The Garner."-" Animal World.""The Naturalist."-" Proceedings of the Liverpool Geologists' Association."-"The Midland Naturalist."-" Journal of the Quekett Microscopical Club."-"Catalogue of Collins' 'Special' Micro Slides."-"The Lost Voice." (Medical Battery Co.) "The American Naturalist."-" Proceedings of the Academy of Natural Sciences, Philadelphia."-K. F. Koehler's Antiquarium, Catalog. No. 428.-"British Moss Flora," Part IX. &c. &c. &c.

COMMUNICATIONS RECEIVED UP TO 11TH ULT. FROM:E. A. S.-W. C.-J. P.-W. G. W.-H. G.-J. R. B. M.M. B. G.-T. E. T.-M. E. T.-F. J. R.-T. W. H.-C. C. A. -A. G. W.-T. D. A. C.-W. H. H.-J. H.-J. G. O. T.— W. H.-P. F. L.-J. W. G.-H. L.-A. J.-W. E. D.F. H. P.-H. W. C.-E. W.-W. K. S.-F. W. E. S.-C. S. -E. D. M.-S. M. M.-J. M.-A. D.-J. B.-H. W. C.-H. -W. R. W.-H. M.-H. W. V. B.-J. T. R.—A. K.—J. C.— J. B.-J. E.-M. E. T.-W. A. C.-A. W. F.-J. A., jun.G. R.-J. M.-C. J.-S. J. H.-J. S., jun.-E. A.-G. C.W. S.-J. B.-G. A. B.-J. B.-F. C. K.-A. P.-C. C.E. H.-W. H. H.-W. S.-J. W.-J. E. L.-J. I.-R. S.W. M.-C. F. W.-W. P. E.-D. Ö.-G. O. H.-F. H.J. L.-S. H.-F. R. R.-G. S.-C. C.-F. G. F.-J. R. R.L. J.-H. P. D.-E. W., &c. &c.

other order shows, from the egg to perfection, a greater diversity of form, or more quaint embellishment.

The division Anoplura, commonly known as lice, are parasitic on mammals and birds. The plate represents the eggs of the species infesting the feathers of the vulture. The number of varieties is very extensive, and the egg necessarily greatly diversified in configuration. Many are beautifully sculptured, and provided with contrivances in the shape of covers and lids. Almost every bird has a distinct variety, some two or three, and different forms of egg may be found in distinct and separate localities, in the breast and neck, and on the under side of the primary wing feathers. Birds in captivity

in shape and adornment, well exemplified in a beautiful specimen of a wood mite of the genus Oribata, procured from Mr. C. Collins, jun., of Harlesden. It presents an extraordinary appearance; the development is, egg, larva, nymph, and the adult male and female. The nymph changes, or partly moults its skin, four or five times, carrying the cast skins on its back overlapping each other, and being necessarily of various sizes they give the appearance of its being surrounded with a series of flounces. The creature in this condition seems tricked out with a general assortment of frippery and furbelows. The reader is referred to Mr. Michael's papers, and beautiful plates on this interesting species in late numbers of the "Journal of the Microscopical Society."

Those who have not access to the writings of Nicolet, Claparède, C. L. Koch, and others, on the Acarina, can procure a cheap handbook, "Economic Entomology; Aptera," by Mr. Andrew Murray, published by Chapman and Hall, by order of the Committee of Council on Education. It is lavishly illustrated with typical forms, well indexed, and forms a valuable key of reference to more exhaustive research.

Crouch End.

TEETH OF FLIES.

By W. H. HARRIS.

No. VIII.

"FUCELLA FUCORUM," Fallen.

HIS fly was taken on debris cast up by the tide

tribe escape. Specimens of the rarest beauty may be obtained from the pheasant.

Of the Acarina, or mites, a wide and interesting field is open to the young microscopist. Found wherever there is decay and mouldiness, even in the cavities of the bones of skeletons, they may be regarded as ubiquitous. Many are extremely curious No. 252.-DECEMBER 1885.

but may, very probably, be taken in other situations if diligently searched for. There is nothing very peculiar in its general appearance to attract attention, and it is therefore rather difficult to describe satisfactorily, so that it may be recognised by the collector. It is a rather small fly, being not more than about a

X

quarter of an inch long. The thorax is of a drab or greyish-brown colour, with a fairly well-defined stripe of a slightly darker shade centrally situated. The dorsal portion of the abdomen is slate, or lead colour; the ventral, a trifle lighter. Each segment of the abdomen bears two spots of a darker hue, but which disappear on looking at the creature with the head pointing towards the observer. The thorax and abdomen are fairly clad with tolerably short hairs, the legs are of the same colour as the abdomen, the eyes a chocolate brown. The proboscis, for about half its length, is fleshy; the remaining portion, towards the extremity, being considerably harder, but scarcely chitinous. When dealt with microscopically, it will be found that the lobes of the labium, although small, are capable of being expanded, and then

impression that a minute molar is being observed. These are all rather dark in colour, and, for the size of the creature, very strong.

A modification of the basal portions of the pseudotrachea form the secondary and third sets of teeth. The bases spring from different parts, and become united as they approach the free end. They are very thin and delicate in structure. On comparing this example with preceding illustrations, it will be found to be by far the most minute yet dealt with, yet a comparatively powerful set of organs are presented; in fact, it would appear that the size of a fly has practically little to do with the general arrangement beyond limiting the size of these organs, but that the nature of the food has probably a much closer bearing on the subject.

reveal a rather interesting set of organs of dentition. These consist of primary, secondary, and third sets of teeth in some portions of the mouth. Viewing them in a lateral position, the primary set are six in number, the two marginal members being of the same type as the blow-fly; then follow on one side (which in its natural position is the fore part of the mouth), two teeth somewhat similar, yet presenting a slight change in form, inasmuch as one of the two points which terminate the organ is considerably longer than the other. One tooth of this form also succeeds the lateral one at the back of the mouth, but it will be observed the long point is here reversed. The remaining tooth of the primary set is rather remarkable, as it bears three points, and, when looked at with an eighth of an inch power, conveys the

I

PRESERVATION OF THE

EYESIGHT.

OBSERVE with great pleasure

that one of the Christmas Annuals has been printed on green paper with the type in blue ink, with the praiseworthy intention of saving the eyesight of readers.

The subscribers to SCIENCE-GOSSIP probably use their eyes more diligently than most persons, both in reading, drawing, working with the microscope, and examining minute objects; this is a question therefore that interests them nearly.

I think it well to point out that, while the book printed as I have described may be better than similar works printed upon dead white paper, the colours of both the paper and the type might be greatly improved. The paper is too much of a bluish-green, and the ink is too bright a blue. Were the paper more of a yellowish-green, and the type dark olive-green, the result would be much more restful to the eyes. I find it is a great benefit to read this book through glasses of a smoky brown tint; the letters appear a less vivid blue and are much sharper defined. Furthermore, a great benefit might be gained by using heavier type, that is, not larger letters, but letters with the fine strokes thicker than they are usually made.

I believe the publishers of SCIENCE-GOSSIP have already paid some attention to this question, and I trust it will one day bring forth fruit.

JOHN BROWNING.

WE have received a series of six slides from Mr. H. Vial, Crediton, containing admirable anatomical sections, beautifully mounted.