SCIENCE- G OSSIP. 



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m 



conducted by p. shillington scales, f.r.m.s. 



Preparing small Marine Invertebrates.— 

 The following method of preparing small marine 

 invertebrates for microscopic study may be of 

 .service to some of our readers. It was originally 

 contributed to the " Journal of Applied Micro- 

 scopy " by Mr. H. P. Johnson, the aim being to 

 retain as fully as possible the natural form, trans- 

 parency, and colouring, and at the same time to 

 Tiave the specimen instantly accessible for re- 

 examination. The specimen is placed on a slide 

 in a few drops of pure sea water, and slightly com- 

 pressed with a cover-glass provided with wax feet. 

 The compression can be quite accurately regulated 

 "by pressing down the wax feet at the corners of 

 -the cover-giass, or prying up the cover-glass a 

 little at one or more corners with the point of a 

 rscalpel. If the specimen is a worm, it will contract 

 .at first ; but afterwards will usually become fairly 

 extended. After two or three houis the worm, 

 although still living, becomes almost perfectly 

 quiescent, A few drops of a i per cent, solution 

 of formaldehyde are then run under the cover- 

 glass, its flow being hastened by draining away 

 with bibulous paper an equal quantity of water at 

 •the opposite side. The worm should die in a fairly 

 •extended condition. A sufficient quantity of 

 formaldehyde should be ran under to displace all 

 the sea water. After an hour or so the gradual 

 replacement of the formaldehyde with glycerine 

 may begin. Mr. Johnson has always used un- 

 diluted glycerine, but suggests that a mixture of 

 equal parts of glycerine and water might be safer 

 for very delicate objects. The glycerine is applied 

 in the same way as the formaldehyde, but more 

 gradually — only two or three drops at a time. 

 After the specimen has become completely sur- 

 rounded and permeated with pure glycerine, the 

 mount is sealed with Venice turpentine in the 

 manner explained in Lee's "Vade Mecum," fifth 

 -edition, p. 291. Preparations keep almost inde- 

 finitely without sealing, but with the obvious dis- 

 advantages that the glycerine is likely to flow over 

 "the slide in moist weather, and a mist gathers on 

 the cover-glass. The preparation should be flat at 

 .all times. This method has been found to meet 

 all the requirements of the case for small Annelids 

 and Echinoderms, and would probably be equally 

 successful for a wide range of minute animal 

 forms, excepting always those with impermeable 

 ■chitinous integuments, like the Arthropods. Syl- 

 lidae and other small Polychetes up to a length of 

 four or five centimetres have been successfully 

 treated, and preparations made three years ago are 

 as beautiful and instructive as at first. 



Demonstrations of Microscopic Manipula- 

 tion. — Mr. C. Baker informs us that he has decided 

 to set aside four afternoons in each month from 

 October to the end of June for the demonstration 

 of microscopic manipulation. These demonstra- 



tions will be given on the first and third Fridays 

 and second and fourth Tuesdays, from 3 to 6 P.M. 

 Each demonstration will consist of an exhibition 

 of about eight microscopes, together with illustra- 

 tive diagrams ; and the instruments will be set up, 

 ready for inspection, at the times stated, so that 

 those who have but a short time at their disposal 

 will not be delayed by preliminary preparations. 

 Three of the demonstrations will deal with illumina- 

 tion, one with the comparison and testing of objec- 

 tives, and two with the various methods of recording 

 observations. Further particulars can be obtained 

 from Mr. C. Baker, 214 High Holborn, W.C., and 

 we need only add that the demonstrations will be 

 free to all, and no obligation to purchase is in- 

 curred by those availing themselves of the offer. 

 It cannot ba too strongly insisted upon that the 

 modern microscope is essentially an instrument of 

 precision, and requires education in its use if its 

 capabilities are to be taken full advantage of. We 

 hope, therefore, that these demonstrations may 

 prove successful. 



C. Baker's Slide Lending System.— The 

 system of slide lending — initiated, we believe, by 

 Mr. C. Baker, and since adopted by other firms, 

 such as Messrs. Watson & Sons, of London, and 

 Mr. Abraham Flatters, of Manchester — was a 

 departure that had much to recommend it. Mr. 

 Baker's system, in brief, is that for a subscription 

 of 21s. the subscriber becomes the recipient of 

 twelve deliveries of twenty slides each, post free 

 both ways. These slides can be arranged for 

 delivery at stated times — say, fortnightly during 

 the winter months, or the time of receipt and 

 return can be left to the varying convenience of 

 the subscriber. The choice of slides is most com- 

 prehensive ; in the list before us we note twenty- 

 five sets of diatoms alone, and four sets of bacteria. 

 The mere examination of slides, however, whether 

 arranged for a definite purpose or not, falls far 

 short in interest and in educational value to the 

 same slides accompanied by the necessary descrip- 

 tions and explanations Kecognising this, Mr. 

 Baker has now arranged that full descriptions shall 

 accompany the slides lent, and has given us the 

 opportunity of perusing several of these sets of 

 detailed notes. The scheme is excellently carried 

 out by competent writers, though the work entailed 

 thereby must have been considerable, as the notes 

 run in each case into many pages. For instance, 

 a set of twenty slides dealing with bacteria is 

 accompanied by a succinct and carefully-written 

 introduction to their study, after which follow 

 detailed descriptions of the respective slides, so 

 that the examination of each becomes a little 

 lesson in itself, the methods of examination 

 and, in certain cases, of preparation not being 

 omitted. Another set of twenty slides deals with 

 Mollusca, and in the accompanying descriptions 

 we recognise a well-known writer on marine 

 zoology. The following extracts will show the 

 nature of these notes. Dealing with the palates 

 of Mollusca, the writer says : " With but two or 

 three exceptions the mouths of Gastropods and 

 Cephalopods are furnished with a tooth-bearing, 

 ribbon-shaped band, variously known as the 

 radula, odontophore, lingual ribbbon, palate, or 

 tongue ; an organ of use in scraping, cutting, 

 boring, or masticating, according to the habit of 

 the particular animal. It is often of very con- 

 siderable length, and consists of an anterior 

 portion working over a cartilaginous swelling, the 



