Dec, 1904.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



307 



•j.itliei iiit;, this last being generally preferable. If 

 fixed in the chromo-acotic mixture it will require about 

 twelve hours for thorough fixation, and twenty-four 

 hours in the formalin. .After chromic acid, the material 

 must be washed in running water or frequent changes 

 for at least one hour, or, better, for three hours. The 

 following simple little piece of apparatus is very useful 

 for washing. It consists of a test-lube fitted with a 

 cork, through which two pieces of glass-tube p.iss. 

 One of these is connected to a water-tap by a piece of 

 rubber tubing, which, in turn, is connected to a piece 

 of glass tubing passing through a cork jammed in the 

 mouth of the tap. .V piece of thin muslin is tied over 

 the end of the other tube inside the jar to prevent the 

 escape of specimens. With formalin no washing is 

 necessary. 



The material being fixed, the next C|uesti()n is the 

 stain. If nuclei are the only details required, 

 Haemalum will be the best to use. It should either be 

 used strong for fi\e minutes, or diluted (i cc. to 50 cc. 

 of water) for twenty-four hours. The staining must 

 be carefullv watched in both cases. Overstaining may 

 be remedied bv water acidulated (.1 per cent.) with 

 hydrochloric acid, but the method is somewhat risky. 

 The other methods of staining are as follow : — .Stain 

 with iron alum solution for three hours, wash in 

 running water for one hour. Stain in Hacmatoxylin 

 solution for six to twelve hours. Now comes the 

 delicate part, for the tissues are much overstained, 

 and must be washed in the iron solution till the details 

 are brought out, examining with the microscope the 

 whole time. Immediately the details are out (gener- 

 ally in about a quartcr-of-an-hour), the decolourisation 

 is stopped by placing the object in tap or rain water. 

 \ow place some water in a watch-glass and add 5 per 

 cent, of glycerine. Transfer the algfe to the dilute 

 glycerine and cover it with an inverted watch-glass, 

 to prevent dust without checking evaporation. 

 Leave until the glycerine is thick enough for 

 mounting, mount in a shallow tin cell in just enough 

 glycerine to fill the cell (this requires some practice), 

 seal with gold size, and when dry ring with Brunswick 

 Black. In some cases a contrast stain may be de- 

 sired. This can be obtained by placing the tissue in 

 the eosin solution for 30 seconds or less, pre\ious to the 

 transference to the 5 per cent, glycerine. 



Notes and Queries. 



Resolution of Amphlpleura peilucida. 



Mr. C. Mostyn (of Kamsgate) writes: Your paragraph in 

 " Knowledge " on resolving .Aniphipleura induces me to 

 describe a method I have lately hit upon, which may possibly 

 not be known to all microscopists. It has the merit of extreme 

 simplicity, not even requiring a sub-stage condenser, or, in 

 fact, any extra appliance whatever, except a sutTicientlv power- 

 ful source of light, and giving the most brilliant resolution 

 ("false resolution," so called, of course) that I have ever 

 obtained, even with immersions and condensers of great N.A. 

 It happens that my microscope (a " Star ") has the very useful 

 fitting of a mirror that can be swung up above the stage for 

 opaque objects. It occurred to me to experiment in the direc- 

 tion of obtaining a " dark ground " or " opaque " illumination 

 with high powers, preferably immersions, by concentrating 

 light on the film of immersion fluid. I tried, among other ex- 

 periments, a slide of Angulatum, mounted in realgar, with a 

 y/' water immersion. N..\. fi8, and sunlight. The result was 

 the most beautiful exhibition of the diatom I have ever seen. 



The diatom, by a httlc c.u'eful handlin.i^ul tlu' uiinur, aijpiaied 

 of a brilliant emerald colour on an ink-black grounil or a 

 light ground could be had at will — and with excellent definition 

 and resolution, free from fog or dilfraction etlcct. This success 

 induced me to try upon Amphiplour.i and Frustulia Saxonica, 

 both of which were most brilliantly resolved. I fancied I 

 could, on some valves, detect the longitudinal stri:c of Amphl- 

 pleura as well ; but the want of a rotation to the stage pre- 

 vented me from examining the valves in the best manner. I 

 may add that the objectives, with a dry condenser of N.A. fo, 

 had hitlierto failed to give resolution, try as I would, with or 

 witliout stops, though an oil lens of N..\. i'25 would do it easily. 

 I then tried a /^eiss ._,'„" — an old water-lens, whose N.A. does 

 not, I think, exceed no — and it resolved Amphipleura etpially 

 well. I have seen m.any expert hands take halfan-hour to 

 effect a satisfactory display ; a minute or two is the outside 

 required with my plan, given a sutlicient amount ol light, .^n 

 ordinary microscope lamp, with halfincli wick, is not powerful 

 enough. Of course, a bull's-eye can be used instead of a 

 mirror ; but it is not nearly as easy to manage. 



I have been told that mine is merely a re-discovery of the 

 " Bramhall Illuminator," but that was a slip ot looking-glass 

 placed below the slide, and on a dilferent principle altogether, 

 though, I believe, very effective in the preimmersion days. I 

 shut off all light from below the slide altogether, with a closed 

 iris. 



Galls on Oak-leaves. //. 11'. Wntuii, llitinhii'iirth. 



The brown gall on the oak-leaf you sent is aCynipidgall, 

 th^l oi Nciiyotfrus Icnticiiltifis. The gall appears in July and 

 matures in September, falling to tlio ground about the 

 cud of that month or the beginning of (October. This autumn 

 generation is parthenogenetic, but another and a sexual 

 generation appears in the spring in quite (lilfer('nt spherical 

 galls known as Spatluxtistcr baccarnm. The gall on the midrib 

 of the same leaf is Ntui-otenis osti-ciis, whilst the gall with a 

 depressed centre on the other oak leaf is Sturi)ieriis numis- 

 inatis, which matures with N. Icntituhiris. These and many 

 other galls were exhibted by Mr. V.. R. Hurdon, of Sidney 

 Sussex College, at the last meeting of the 15rilish Association 

 held in Cambridge, and Mr. Hurdon has been good enough 

 to name the above species for me. Vou will find the sul)ject 

 dealt with in " Alternating generations; a biological study of 

 oak-galls and gall-flies," by Hennaini Adler, translated by 

 C. R. Straton, and published by tlie Clarendon Press in 1894. 

 In this book you will find instructions as to rearing the flics — • 

 the eggs themselves can be easily dissected out if you wish to 

 do so. I do not think you could turn your attention to a more 

 interesting branch of study or one offering more opportunities 

 for original work, as the whole subject has been neglected by 

 all but a very few workers. 



John Hume, Ncwcastkon-Tync. The gall you sent is that of 

 Neuroterus Iciiticularis mentioned above. 



//. 11'. Harvey, Norfolk. What you thought to be a fungus 

 is the same gall. With regard to the •' second sting" you 

 speak of, the drawing you send is not sufficient to enable me 

 to pronounce an opinion, but these stings are generally made 

 of a couple of darts which join together so as to form a canal 

 down which the poison passes into the wound. Is it not 

 possible that you have split one of these, or even damaged 

 their sheath, and so formed an erroneous impression ? 



Derivation of Names of Diatoms. 



Rev. W. Hamilton Gordon, of Fareham, Hants, would be 

 glad if any reader could give the derivation of the names 

 Sitrirella and Nil:ssihitt as .applied to diatoms. I think there 

 can be no doubt th.it the latter diatom was named after the 

 worm of the same name, but that does not bring one much 

 nearer. With regard to the distribution of diatom material, 

 I am dependent entirely on the generosity of such readers of 

 my notes as have material of one sort or another which they 

 are good enough to send me for distribution to others. 



[Communicationi and enquiries, nn Muroscoficiil matters are invittd, 

 and shuuld lie addressed to F. ShiUini^lun Scales, "Jersey, "St. 

 Barnabas Road, Cambridge.} 



