2S2 



KNOWLEDGE. 



July. 1911. 



on the image. Mr. Nelson summed up the result by one word 

 — " Fog." — The simplest condenser, even a single lens so used, 

 gave a better image than could be obtained with ground-glass. 



Sir D. Brewster, in 1S36, was the first to employ colour 

 screens in microscopy. Mr. Nelson recommended the use of 

 a screen composed of a piece of peacock-green glass combined 

 with a very light blue for visual daylight work, and for lamp- 

 light a piece of thicker peacock-green glass combined with a 

 blue glass of the tint of the blue cornflower. Reference was 

 also made to the various forms of Gifford's screen and to that 

 used by Dr, Miethe. 



One other form of illumination dealt with by Mr. Nelson is 

 that of using part of the spectrum. A prismatic spectrum is 

 brighter than that given by a diffraction grating, although on 

 the other hand, the dispersion obtained with a fourteen 

 thousand line grating between E and G in the first order is 

 more than double that of an ordinary flint-glass prism. 



The Chairman in asking the meeting to pass a very hearty 

 vote of thanks to Mr. Nelson, made some very appreciative 

 remarks on the " M " series of screens issued by Messrs. 

 Wratten and Wainwright. He considered them almost 

 indispensable to the careful worker, as they afforded full 

 control of the colour of the lighting and consequently of the 

 amount of contrast obtained with all classes of coloured 

 objects. 



THE ROYAL MICROSCOPICAL SOCIETY. — Mav 

 17th, 1911. H. G. Plinuner. Esq., F.R.S., President, in the 

 chair. Mr. J. E. Barnard made a connnunication on a 

 method of disintegrating bacteria and other organic cells. 

 The author first mentioned that bacterial to.xins were of two 

 kinds, extra-cellular and intra-cellular. The former were 

 excreted into the medium, e.g., beef broth, in which the 

 organism was cultivated, so that by a process of filtration the 

 organism could be removed and the toxin was obtained in the 

 filtrate, but the majority of pathogenic micro-organisms did 

 not excrete their toxins, at least to any great extent, and the 

 toxins were retained within and formed integral parts of the 

 cells of the organisms. 



One method of obtaining these toxins was to mechanicallv 

 disintegrate the bacterial cell, so that the cell contents were 

 expressed, and the apparatus described accomplished this. 



It consisted essentially of a containing vessel in which, by a 

 suitable rotation of steel balls, the organisms were crushed. 



The principal conditions to be fulfilled in such an appliance 

 were : — 



(1) ."Vpproxiuiately e\ery cell should be brought under the 

 grinding action. 



(2) Little or no rise of temperature should take place. 



(3) The disintegration should be carried out in a vessel 

 which was sealed so that, when dealing with pathogenic 

 organisms, none could escape at any stage of the process. 



These conditions were, in the main, complied with in the 

 apparatus described. Experiments indicated that by this 

 method the cell juices were obtained unaltered, and so were 

 suitable for investigation on the chemical composition and 

 properties of the bacterial proteins and other cell constituents. 

 Also that, after the grinding process had been carried on for a 

 sufficient time, practically no cells remained which could be 

 properly stained by any recognised bacteriological method, and 

 which, therefore, conld be regarded as whole cells containing a 

 normal quantity of cell juice. 



Mr. James Murray presented a third portion of his report 

 on the Rotifera observed by the Shackleton Polar Expedition 

 of 1909, dealing with the new species, and so on, from the 

 Pacific Islands. He said that in Fiji fifteen Bdelloid Rotifera 

 were collected, in Hawaii twenty-four, ten species being 

 common to the two groups of islands. 



In Fiji two new species were dislingnished. Callidina 

 pacifica and Hahruiroclia nodosa, the latter previously 

 known, as a variety, in India, and elsewhere. 



In Hawaii there were no peculiar species, but some very 

 distinct varieties. 



In the various Pacific Islands there have been recorded 

 thirty-one species of Bdelloids. 



The attention of the Fellows of the Society was then directed 

 to the collection of specimens of Pond Life, which had been 

 arranged for the evening. 



OKXITHOLOGY. 



By High Boyd \\.\tt. M.B.O.U. 



THE DISTRIBUTION OF THE NIGHTINGALE IN 

 GREAT BRITAIN DURING THE BREEDING SEASON. 

 — Discussion of this subject is revived by an article contributed 

 to the June number of British Birds (Vol. V., No. 1, pages 

 2-211. by Mr. N. F. Ticehurst and the Rev. F. C. R. Jourdain. 

 The chief value of the paper lies in the carefully worked 

 out details given under those counties in which the distribu- 

 tion of the species is local, or which mark the limits of its 

 range in England and Wales. This faunistic information is 

 very valuable and full, and summarises present-day knowledge 

 on this part of the subject, making clear the well-known and 

 curiously partial character of the bird's distribution. Com- 

 menting on the last-named point, the writers express the opinion 

 ■■ that the real obstacles which prevent the general distribution of 

 this species over the greater part of England and Wales are 

 the ranges of elevated land, which it instinctively avoids." 

 This seems adequate only in so far as it is limiting and 

 negative in character, and the condition laid down is in no 

 way peculiar to the Nightingale. Height of land is a factor 

 which affects the distribution of species generally, but many 

 other considerations come in. That the Nightingale is not 

 found on elevated land, and that its distribution is restricted 

 or limited by such elevations, may account for its absence 

 there ; but this reason seems an incomplete explanation of 

 its presence in its frequented haunts and known stations, and 

 not in contiguous places where the conditions are apparently 

 similar. It would seem that Professor Newton's judgment must 

 still stand. \iz. : — " No reasonable mode of accounting for the 

 partial distribution of the Nightingale has hitherto been 

 propounded " \" Dictionary of Birds." 1903-6, pages 339-3401. 



THE BIRDS OF ST. ALBANS.— This famous old 

 city, like the county in which it is situated, has rather a 

 meagre avi-fauna, due, chiefly, to the absence of maritime 

 conditions. Nor does there seem to be any great fly-line of 

 migrants across the county from which records might be 

 gathered. Hertfordshire birds number about two hundred 

 and ten species in all, and the St. Albans list includes one 

 hundred and twenty-eight of these. Mr. W. Bickerton gives a 

 good account and classification 'for the city and a radius 

 of five miles around) in a work entitled "St. .-Mbans and 

 its Neighbourhood" (1911), published by the Hertfordshire 

 Natural History Society, in connection with the .\nnual 

 Congress of the South-Eastern Union of Scientific Societies 

 recently held in that city. Mr. Bickerton's article (pages 

 240-243) lays a sound basis for further observations and 

 bird-study in the district. 



ACCOUNTING FOR THE ROOK.— The thinning-out 

 of the Rook, recommended by some authorities, is not neglected 

 in some districts. For instance. Mr. C. C. Ellison, 

 Bracebridge, Lincoln, writes to The Field that one day's 

 shooting each year for thirty years on the same estate has 

 produced 20,793 Rooks. The biggest bag was 1,220 to seven 

 rifles : the best was 1,210 to two rifles only. Mr. Ellison adds 

 that there are probably not half the Rooks in the country now 

 that there were in 1H80. 



TH£ BOYD ALEXANDER COLLECTIONS.— The 

 great collections formed by the late Mr. Boyd Alexander on 

 his .African expeditions, and bequeathed by him to the Natural 

 History Museum, South Kensington, have now been h.anded 

 over to that institution by his executor. Mr. Robert .\lexander. 

 They comprise nearly four thousand bird-skins of .African 

 species, and include the type-specimens of no fewer than eighty 

 species. 



