May. 1915. 



KNOWLEDGE. 



153 



(2) Arrange the radula on the slide, after clearing away 



the adherent membranes, i.e., the lining of the 

 odontophore sac. 



(3) Cover the radula with a drop of acidified perman- 



ganate solution. The best formula for use will 

 vary with circumstances, but that employed 

 in the making of autochromes serves very well. 

 The unci- — and, to some extent, the whole 

 membrane — are now seen to turn vellow, brown, 

 and, finally, black. 



(4) Now wash off the permanganate, which has ful- 



filled its oxidising function, with distilled water. 



(5) Cover the radula with a drop of oxalic-acid solution, 



which will gradually decolorise it, with evo- 

 lution of C0 2 . 



(6) Wash thoroughly with distilled water and again 



soak in dilute acetic acid. 



(7) The radula can now be stained in a weak solution 



of dahlia in one per cent, acetic acid. The 

 advantage of using a weak solution is that the 

 progress of staining can be watched ; but over- 

 staining does not very readily occur, because 

 the oxidation is limited to the external layers 

 of the chitin, and thus a transparent effect can 

 be obtained. 



(8) Dehydrate, clear in oil of cloves, and mount in 



xylol balsam. 

 Though this process seems long, it is, in reality, quite 

 simple and easy, and the effect can be seen at each stage, 

 so that there need be no doubt about the final result if the 

 operations are conducted with reasonable care. Such a 

 preparation may be regarded as permanent : it requires no 

 ringing. Some other stains can be used in place of dahlia, 

 but I have not yet found any equally satisfactory. The 

 object looks bluish-violet by daylight and violet-red bv 

 lamplight. It is easily photographed on the Ilford chro- 

 matic plate with a yellow or green screen. Personally I 

 prefer the latter, as giving a little more contrast. The full 

 aperture of the objective (if it is of a good make) can be 

 used. 



Hydrolysis of the chitin also may be brought about by 

 various reagents, and renders the radula permeable to many 

 stains, such as acid fuchsin, indigo carmine, and brilliant 

 black. The various methods of inducing hydrolysis which 

 I have tried have, however, been much more uncertain and 

 tedious than the superficial oxidation process described 

 above. E. W. Bowell. 



THE PHOTOMICROGRAPHIC SOCIETY.— In the 

 year 1911 the Photomicrographic Society was started, 

 and since that time it has been actively at work. The 

 ordinary meetings are held at King's College Bacteriological 

 Laboratories, 62, Chandos Street, London, W.C, at 8 p.m. 

 on the second Wednesday in the month, from October to 

 May inclusive. At these gatherings visitors are welcomed. 

 There are, besides, " members' evenings " — usually on the 

 fourth Wednesdayin the month — for membersonly. Hitherto 

 the proceedings of the Society have been issued, but they 

 have not been printed. Now we are able to welcome them in 

 ty-pe as The Journal of the Photomicrographic Society (price 

 to non-members, 3s. 9d.). The present instalment contains 

 an account of several ordinary meetings, and the papers 

 read at them, including one by Mr. J. E. Barnard, on 

 " Colour Screens." This should be of particular use to 

 those who are photographing through the microscope, 

 as it is most practical. The absorption spectra of some of 

 the filters are given as plates. There is also a paper, bv Mr. 

 Martin Duncan, on " Studies in Marine Biology," and one, 

 by Mr. C. A. Bunnin, on " Colour Sensitive Plates and their 

 Uses." Beginners in the work will find Mr Wellesley 

 Harris's " Hints on Photomicrography " most helpful. 

 The success which Mr. Wellesley- Harris obtains with the 

 methods which he uses and describes can be gathered from 

 the illustrations, which we have been kindly permitted to 

 reproduce on page 148, and as in his paper he gives very 

 full details as to lighting, lenses, camera extension, and so on, 



he makes it all the easier for those who take up photo- 

 micrography to follow in his footsteps. We might add that 

 the subscription to the Society is seven shillings and sixpence 

 for the session, and includes two issues of the Society's 

 Journal. The Honorary Secretary is Mr. J. E. Bradbury, 

 1. Hogarth Hill, Hendon, X \Y. W. M W. 



HAIRS OF THE LARVA OF AX AXTHREXUS — 

 On unpacking a small consignment of insects from Xatal 

 I found amongst them the living larva of a coleopterous 

 insect, probably that of an Anthrenus. Shortly afterwards 

 it entered the pupa state, and in due course a small beetle 

 about one-ninth of an inch long was developed. The 



a 



a x 50. 



310. 



d x 310. 



c ■ 50. 



Figure 131. 



thorax and elytra of this were covered with beautiful 

 scales, white, dark brown, and orange-coloured, arranged 

 in symmetrical patterns. Having mounted the exuvium 

 in Canada balsam, I found, on careful examination, a 

 considerable difference between it and that of the species 

 only too well known to insect collectors in this country. 

 The body in each case was covered with delicate pointed 

 hairs, the majority of which were fringed throughout 

 their entire length by minute secondary hairs see Figure 

 131c), but from the margin of each segment, except the 

 first and last, in the Xatal species there extended a large 

 number of spear-headed hairs (see Figure 1316), somewhat 

 similar to those which used to be mounted and sold under 

 the name of " Hairs of the larva of Dermestes,'' although 

 it is well known to entomologists that the genus Dermestes 

 does not possess them. In the English variety these hairs 

 (see Figure 131 d) were only to be found near the tail A com- 

 parison between them showed that those of the former were 

 smaller, and that the whorls with which the shafts were 

 adorned were closer together and less prominent, whilst 

 the heads of the spears differed in shape at their bases, and 

 were proportionately longer, though not quite so broad Two 

 dense tufts, each consisting of not fewer than two hundred 

 hairs, proceeded from the lateral margins of the last segment 

 but one, and extended much beyond the last segment itself 

 The feet in each case carried a single claw, but those of the 

 English species (see Figure 131«) were larger and st: 

 than those from Natal (see Figure 131a) ; the mandibles 

 in each case were simil.it in size and shape. A still smaller 

 beetle from China, obviously an Anthienus. is a 

 with black scales of the fame shape as those of the 

 species. R- T. L. 



THE QUEKETT MICROSCOPR VL CLUB.— At the 

 five hundred and sixth ordinary meeting of the Club on 

 Tuesday, March 23rd, Mr r D Soar r.-.id a risumi of a 

 paper by Mr. Williamson and himself on " British Hydra- 

 carina, genus Lebertia" Mr J W Cordon showed and 



