ArcvsT, 1004.1 



KNOWLEDGE 8z SCIENTIFIC NEWS. 



195 



mountins; in pillboxes were described. Another point ol 

 interest w.isthe coniinj? down of the objective to snch size as 

 to admit as imieh, and no more, light than could be utilized 

 by the back lens : this reduction of the front of the objective 

 facilitated the illumination of opaque objects. Professor 

 J. D. Everett read his paper, entitled " .\ direct proof of 

 .\bbe"s theorem on the microscopic resolution of gratings." 

 In the subsequent discussion Mr. J. W. Gordon, Mr. Conrad 

 Beck, and Mr. Kheinberg took part. Mr. Beck explained 

 .\bbe"s experiment with a grating on .the stage showing doub- 

 ling of the lines by means of a triple slit in the focal plane of 

 the object glass. This he had brought at Professor Everett's 

 request in illustration of the paper. Mr. Kheinberg followed 

 with some remarks on the influence on image gratings of phase 

 difference among their spectra, which he illustrated by an 

 arrangement he had prepared of a microscope that showed the 

 movement of lines in the image of a grating by creating a 

 phase difference amongst the spectra in the back focal plane 

 of the objective by means of an .\bbe glass-wedge compensa- 

 tor. Mr. F. \V. Millett's paper, the 16th of the series, on the 

 recent Foraminifera of the Malay .\rcliipelago was taken as 

 read. Mr. F. Enock then gave his lecture on '■ Nature's 

 Protection of Insect Life," which was illustrated by a fine 

 series of lantern slides of colour-photographs of living insects. 

 The following were elected Honorarv Fellows of the Society : 

 Gaston Bonner, Jacques Brun.Vves Delage, S. Ramon yCajal, 

 B. Renault, J. J. Harris Teall, Sylvanus R. Thompson, and 

 M. Treub. 



Quekett Microscopical Club. 



The 415th ordinary meeting of the Club was held on 

 June 17, at 20, Hanover Square, \V., the President, Dr. E. J. 

 Spitta, V.P.R.A.S., in the chair. An unusuallv large number 

 of new members were balloted for. .Mr. C. D. Soar, F.R.M.S., 

 read a paper descriptive of two new Fresh-water Mites, 

 Psiiidd/cltria scoiirfieldi, discovered in Cwmm Glas, North 

 Wales, by himself, and Midccpsis crassipcs. found at Oban by 

 Mr. Taverner. The President then gave an interesting lecture 

 and demonstration " On a Method of Suiting Screens for the 

 Photomicrography of Stained Bacteria." He was assisted by 

 his son. Dr. Harold Spitta, who exhibited a number of lantern 

 slides and diagrams illustrative of the method and its results, 

 and by Mr. Conrady, who manipulated a second lantern fitted 

 with a large spectroscope, by means of which a series of 

 beautiful and interesting spectra were thrown upon a sepa- 

 rate screen. After comparing and contrasting the differences 

 between the eye and the photographic plate in the matter of 

 colour sensation, Dr. E. J. Spitta went into a comparison of 

 the various orthochromatic plates upon the market. By test- 

 ing each plate under long and short exposures with a spec- 

 troscope, he found a wide difference in their relative sensibility 

 to colour, a difference which he illustrated by means of photo- 

 graphs of the spectrum taken on each kind of plate. Having 

 ascertained by this means the limit of their sensitiveness in 

 the presence of colour, which he termed the " eye " of the 

 plate, he was enabled to construct contrasting screens by 

 means of which the maximum contrast was obtainable. 

 Photographs of bacteria stained with Lofiler'? blue, gentian 

 violet, and carbol fuchsin, the three principal bacteriological 

 stains, were exhibited, taken with and without the contrasting 

 screens. The results were most striking, the improvement in 

 detail and definition being very marked. 



H. W. Harvey, Norfolk, 



I would suggest your getting M. C. Cooke's " Microscopic 

 Fungi," which forms a good introduction to the study of the 

 subject. 

 T. H. Astbur>-, Wallingford. 



In answer to your (|uery as to Mr. Warburton's article on 

 "Mites," Mr. Warburtoii says he uses concentrated carbolic 

 acid for clearing. I am aware that this sometimes leads to 

 difficulties in subsequent mounting in Canada balsam, but 

 Mr. Warburton says he has no difficulty with it. With regard 

 to the parasitic growths upon Piiniiis prolifcricornh, if you 

 will send me the Iieetle I will see what I can do with if. 

 .Miss B. B. Bryant, Bath. 



By the blow-fly Calliphora vamiioria is understood. It 

 has a yellow, golden, or white head, brown eyes, black thorax, 

 and blue abdomen with black stripes and long black hairs. 



i'hc tlesh-rtv is S,ii\iipluti^(i caninriu. It has .a head yellow in 

 front, with feathery .intenn;e, reddish eyes, grey thorax, with 

 longitudinal black lines, black abdomen with four square 

 white spots on each segment, .uid bl.ick hairs on .all the body. 

 Dr. Sharp has kindly given nie the following particulars : " By 

 blow-flies and meat-flics I think people mean the same thing, 

 viz., the blue CuUiphoni s. Hut the flc^sh-fly is a very different 

 insect — a grey-striped and black insect with red eyes — Surcoph- 

 af;a carnaria. There is rather a difficulty .as rcg.irds Sarcopliuf^a, 

 because there are different species : though horribly awake they 

 apparently difter greatly in economics, the .S'. carnciria being 

 viviparous. As regards the blow-flies, both Calliphova voiui- 

 toriii and C. t-iytlinici-plui!ii are equally common here; one has 

 a yellow face with black beard on if, th(^ other a black face 

 with yellow hairs. No doubt witli most people they pass as 

 all C. ervthroccphala. Siircopliaga has the abdomen mottled a 

 sort of s<]uare pattern, it has very large pulvilli on the feet, is 

 a quite different shape from Calliphora, and keeps in the 

 countrv on the look out for carcases. There is still a great 

 deal of much interest to be discovered about these coinmon 

 flies, which, though disgusting to most people, are pliysiologic- 

 ally at the top of the animal kingdom." " A List of British 

 Di'ptera," by G. H, Verrall { jnd edition) may be procured from 

 the author, Sussex Lodge, Newmarket. With regard to 

 mounting flies whole, I would suggest your trying a weaker 

 solution of potassium hydrate and longer immersion. The 

 object of this soaking is mainly to dissolve out the contc'Uts of 

 the abdomen, &c., after which the object is washed first 

 thoroughly in wafer and then dehydrated in alcohol, and 

 finally so.aked (for a few days, if necessary) in turpentine to 

 make it transparent, then cleared in clove-oil and mounted in 

 Canada balsam. If this does not prove satisfactory, I would 

 suggest treating the wings separately and mounting on the 

 same slide, or mounting another fly dry fi)r comparison. 

 A. Morley Jones, Ealing. 



Vour query has not reached me before, but you do not 

 say what are the Zoophytes to which you refer. Generally 

 speaking, the method of mounting would be narcotisation by 

 cocaine by gradually adding a one per cent, solution to a 

 small quantity of water containing the specimens, or killing at 

 once by a drop of osmic acid, washing in water, staining if 

 requisite, again washing, and finally mounting in glycerine 

 jelly. 

 George Phelps, Warminster. 



I am afraid the only reference I can give you on the subject 

 of Trombidiid mites is to the article on Mites in "Carpenter." 

 Mr. Michael's monographs in the Ray Society's publications 

 deal only with the Orihatidie and cheese-miles. The forth- 

 coming volume of the Cambridge Natural History will have a 

 short account of the Tromhidiidw, and I understand from Mr. 

 Soar that a number of " Das Tierreich" shortly to be published 

 will contain a full list and description of every species. As I 

 have said to another correspondent, the literature with regard 

 to mites is in a very incomplete state. 

 A. Robinson, Portsmouth. 



An objective corrected for a short tube docs not perform as 

 well with the long tube; but it is so much a matter for a 

 critical eye and critical illumination that I fear I cannot advise 

 you how to ascertain the length of tube for which your objec- 

 tives are corrected if your own work has not shown it to you. 

 I would suggest, however, your obtaining a slide of the pro- 

 boscis of a blow-fly, and,'using the edge of the lamp-flame, 

 carefully focus first the objective upon the slide, and then the 

 lamp flame by means of the condenser, so that with a mode- 

 ratelv low po%ver a distinctly marked band of light lies across 

 the field. The fine hairs on the tip of the proboscis (not the 

 long ones on the edge) are those to be looked at, and the iris 

 diaphragm must be sluit down just enough to cut off any excess 

 of light, and not enough to cause any thickening of the fila- 

 ment-like points of the hairs, or any refraction rings around 

 them. Then use the highest-powered eyepiece you have, and 

 note whether the objective performs best when the tube is 

 fully closed or fully extended. As a matter of fact, nearly all 

 students' series of objectives, whether of English or Continental 

 make, if comparatively recently made, are corrected now for 

 the short tube. 



[Communications and enquiries on Microscopical matters arc invited, 

 and should be addressed to F. Shillington Scales, "Jersey," St. 

 liarnalias Road, Cambridge .] 



