June, 1911. 



KNOWLEDGE. 



235 



hidciis is, in fact, the largest pellet-making species yet found, 

 my exatnples attaining a length of 460 m, when apparently 

 fully grown. But apart from its great size, it may be 

 recognised by the slenderness of the anal segment, and by the 

 length of the foot, the post-anal segment being about twice 

 as long as its average width, and also by a pecuHar ridge-like 

 structure crossing the trochal discs. When feeding the foot 

 was generally extended, sometimes showing the central toe 

 (c.t. Figures 2 and 3), sometimes not. The rather short spurs 

 (s.s.) were held nearly parallel to the body axis. The lateral 

 toes \l.t.) were invaginated as usual. 



A diagrammatic view of the head with corona displayed is 

 given in Figure 1, the cilia of both principal and secondary 

 wreaths, which are quite normal, being omitted for greater 

 clearness. The moderately wide trochal discs are supported 

 on two strong pedicels. Near the centre of each disc the 

 trochal seta-pencil rises from a small prominence from which 

 a low ridge (r. r.) continues to and over the inner margin of 

 the disc, the ridge from either disc dipping to meet that from 

 the other. As these ridges arise at the nerve centre of the 

 discs, I surmise that they protect nerve branches passing 

 towards the median line. I have not seen them so well 

 developed in any other Bdelloid and rarely even rudimentary. 

 Between their junction and the moderately high upper lip 

 (i(./.) is visible a fleshy nexus in.) connecting the pedicels 

 and extending nearly up to the level of the discs. 



In all my specimens, the food- pellets were of unusually small 

 size. The characteristic wildness of the animal is greatly 

 modified if it be kept for a week or so in a small trough or cell. 

 Examples thus confined produced eggs of oval form, but 

 proportionally longer than customary among Bdelloids. The 

 embryo developed very rapidly, and the young rotifer emerged 

 in about six days, about half the usual period. 



David Brvck. 



ON FLUID MOUNTING.— There is no question that 

 with very many classes of objects fluid mounting is the best, 

 as the preparation is shown without pressure or distortion, and 

 the natural arrangement of the parts gives a true idea of its 

 real nature. Many of us, however, bar fluid slides altogether 

 owing to their usual habit of leaking after a short period, and 

 it is to obviate this fault that the present note is given. The 

 first essential of a cemented joint is usually as close a joint as 

 possible with a mininnnn quantity of the adhesive. This, as 

 is ordinarily tried with marine glue, gi\es a perfectly sound 

 joint of the ring to the slide, but owing to the unequal expansion 

 and contraction with temperature changes of the fluid mountant 

 as compared with the glass, the rigid setting sooner or later 

 gives way and the slide is ruined. What is really re(|uired is 

 a cement sufficiently hard to be adhesive, rigid enough to bear 

 handling, yet elastic to stand the trifling differences of volume 

 required with temperature variation. Hence a sufficient 

 quantity of an elastic cement must be used to accommodate 

 by its own variability the necessary changes. Such a cement 

 can be made as follows : — A penny tube of cycle rubber 

 solution, which is rubber in naphtha, is emptied into a four- 

 ounce bottle and double its volume of old gold size added, 

 shaking till thoroughly mixed. This must now be placed on a 

 water bath or anywhere to be heated not beyond one hundred 

 and fifty degrees in order to drive off the naphtha and .any 

 volatile constituent of the gold size. Whilst this is being done, 

 prepare a thick solution of shellac in absolute alcohol (not 

 methylated spirit) and add, when the other solution is naphtha- 

 free, twice its volume of shellac solution as thick as treacle. Stir 

 whilst hot and filter through fine nuislin before cooling. It can 

 be thinned as desired with absolute alcohol. The reason why 

 methylated spirit cannot be used is that the denaturant which 

 evaporates with the spirit may evaporate inwards and be 

 condensed in the fluid mountant, and I have seen many slides 

 spoiled by a milky fog caused by the condensed denaturant, 

 which is not transparent w hen mixed with water any more 

 than methylated spirit is. The quantity required is not large, 

 so absolute alcohol is not prohibitive. 



Use the mountant as thickly as it can be worked to flow and 

 make a heavy ring on the slide. Of course, it is preferable to 

 do a fair quantity at one time. This sets in about fifteen 



minutes and dries reasonably hard in a day. This ensures 

 perfect contact of the cement to glass slip. To cement the 

 rings I take a scraping of soap from the piece in use, and 

 spread it on the turntabf? centre. A ring flatted on coarse emery 

 cloth if metal, or coarse saiidpaper if vulcanite, can be pressed 

 on to the soap and adjusted centrally with sufficient firmness 

 to be cemented all round, leaving a more le\ el ring than can 

 be otherwise obtained. The next day, or later, a thin ring of 

 cement can be put on the slip and the ring adjusted in place. 

 When hardened you will have perfect .contact of cement and 

 glass, with perfect contact of cement and ring, with an elastic 

 layer of cement in between, which is capable of absorbing 

 any small variation under the exercise of pressure. .A. ring 

 fixed in this manner is likely to remain permanent if the further 

 mounting operations are properly performed. 



C. E. Heath, F.R.M.S. 



MICRO -FUNGUS FROM THE JAPAN - BRITISH 

 EXHIBITION. — A friend who visited the .\ino village in 

 the Japan-British Exhibition last year at Shepherd's Bush, 

 happened to pull out a straw from one of the native huts. 

 He found it was rice straw and had been brought from Japan 

 specially for the construction of the huts. Some minute dark 

 spots on a leaf proved on examination under the microscope 

 to be patches of a fungus. It is one of the Puccinias, a genus 



Figure 1. 



Figure 2. 



of which there are very many species, growing on various 

 plants and widely distributed. Dr. Cooke records no less 

 than seventy-eight for Britain alone, " Microscopic Fungi " 

 p.p. 202-212. The well-known " Mildew " on wheat is one 

 of them, P. grant inis, and the example found on the rice straw 

 closely resembles it, though probably, as living on another host, 

 it would be considered a separate species. The patches (sori) 

 are found on both sides of the leaf in this case, and are made 

 up of very numerous double spores, attached to stalks often of 

 considerable length. Figure 1. The mature spore has a thick 

 outer coat of a rich brown colour, and a thinner one within. 

 .\i the apex an opening through the thick coat can be seen, 

 and the lower spore has a similar opening — usually rather 

 difficult to make out — on one side just below the cross wall. 

 Figure 2. Through these openings, on germination taking 

 place, a tube is protruded, the further end of which divides 

 into three or four cells each bearing a very small spore on the 

 end of a short branch. Figure 2. It is these extremely minute 

 secondary spores which propagate the fungus. In many 

 species they do not reproduce a Puccinia such as they arise 

 from, but another form known as " cluster cups," an elegant 

 little fungus well known to microscopists. This may be pro- 

 duced on the same or on a different species of host plant, witfi 

 many variations in the details, for the life history in most cases 

 is very complicated. Immense loss is caused to farmers and 

 horticulturists, as the fungi weaken and even destroy the plants 

 on which they grow. . „ 



THE SCALES OF LEPIDOPTERA.— Some time ago I 

 recei\'ed from a correspondent in South Africa some curious 

 pupae which he had found suspended by threads from one of 

 the branches of a bush. They were sent in spirit which did 

 not seem to have injuriously affected either their form or 

 colour. On examination they were seen to be in different 

 stages of development, the imago in one being apparently on 

 the point of emergence. Upon carefully removing the 

 enclosing membrane from this, I extracted a butterfly which 



