HARDWICKE'S SCIENCE-GOSSIP. 



"3 



made in the title. The proper term to use is photo- 

 micrography, and not micro-photography. The 

 difference between the two is very great ; for, whilst 

 photo-micrography means photographing minute 

 objects enlarged by the microscope, micro-photo- 

 graphy is photographing large objects on a reduced 

 scale on glass slips for examination with the micro- 

 scope. Various views are treated in this manner, 

 and can be bought at the optician's. Mr. Barker 

 seems also to have overlooked one very important 

 point in his ingenious contrivance, viz., stability, or, 

 more correctly speaking, rigidity. It will be seen 

 by the sketch that the camera back is only supported 

 by one of its sides, and that very insecurely by the 

 rackwork and pinion. Now, as a professional pho- 

 tographer of some years' experience, I can answer for 

 the necessity of absolute firmness in all the apparatus 

 connected with photo-micrography, and, unless this 

 is attended to clearness of definition will not always 

 be obtained. This defect might be overcome by 

 attaching a strip of brass to the top of the camera 

 front, having in it a long slot, and when the focus 

 has been determined it could be fastened firmly to 

 the top of the camera back with a milled edge screw. 

 This is very frequently found on cameras which 

 require to be held very rigid. If the focussing 

 arrangement works loosely it must be tightened up, 

 or want of rigidity will be caused by this way. In 

 focussing it is always best to use a focussing-glass, 

 which can be obtained at the photographic opticians 

 for about half-a-crown. Should your readers require 

 to know anything at any time in connection with 

 photography, I shall always be pleased to inform 

 them through the medium of your interesting journal. 

 I trust Mr. D. W. Barker will excuse me for having 

 corrected him. — Roland Whiting. 



"Fixtng" Cell Contents. — Can any one tell 

 me what takes place when the cell contents of animal 

 or vegetable tissue are " fixed " by alcohol or some 

 other liquid ? I suppose the word means that the 

 protoplasm is preserved in its original state un- 

 changed. But I should like to know what is the 

 real nature of the operation of the fixing agent ; also 

 what book there is which explains the reasons of the 

 process made use of in microscopical research. There 

 are plenty of books on manipulation, but I cannot 

 meet with any explanation of processes. — A. P. 



Mounting Fresh-water Alce. — I have tried 

 many mediums for mounting fresh-water algze, and 

 find the best to be a solution of acetate of potash 

 in water. [It does not alter the chlorophyl, and 

 preserves the colour fairly well in most species, 

 and perfectly in some. A fluid ounce of water to 

 half an ounce of the potash is the recipe. Should 

 anything like crystals form in the mount, the solution 

 should be weakened by the addition of more water. 

 Farrant's medium is the next best ; I often use it, and 



produce most satisfactory results ; but the objects to 

 be mounted in it must previously remain for a couple 

 of minutes in the " I, 2, 3," or "Gwa" mixture. 

 The "Gwa" mixture is composed of glycerine 1 

 part, water 2 parts, and alcohol 3 parts. After 

 this preparation the Farrant does not effect much 

 alteration of the chlorophyl. — H. IV. Lett. 



Preservation of Melicerta ringens. — Since 

 this rotifer is often spoken of as being difficult to 

 preserve for any length of time in captivity, it may 

 perhaps be interesting to your readers to learn that 

 I have had it in my aquarium for something like 

 twelve months without any interregnum. Last spring 

 I had only a few, but all summer and up to quite late 

 in the autumn they were very abundant, in numbers 

 far too great to count, but certainly many thousands 

 were to be seen. During the winter they somewhat 

 diminished in number, but are now fast becoming as 

 numerous as ever. My aquarium is only a small bell- 

 glass ten inches in diameter, having in the bottom a 

 small quantity of clay with small stones and sand over 

 it : in the aquarium are growing the following plants, 

 namely Fontinalis antipyretica, ceratophyllum, riccia 

 jlnitans, Lemna minor, the only animal life apart from 

 the microscopical organisms being one stickleback 

 and a few living planorbis. Aspect S.W. Melicerta 

 was accidentally introduced into the aquarium nearly 

 two years ago on a piece of potornogeton crispus, 

 together with Limnias ccratophylli, both becoming 

 abundant upon myriophyllum, but according to its 

 habit this latter plant upon the approach of winter 

 broke up, and the Limnias has never reappeared. 

 So far as my experience may be any guide, fonti- 

 nalis and ceratopyllum are very good plants for a 

 small aquarium ; Riccia also does well. Can any of 

 your readers tell me if Melicerta has ever been pre- 

 served for the same length of time. — J. N. Measures, 

 M.R.C.S.E. 



Note on Ch^tospira Mulleri. — Last month 

 I found chcetospira mitcicola on some chard. On and 

 within the tissues of the same plant was the beautiful 

 animalcule, chcetospira Mulleri. The following extracts 

 regarding the latter from Pritchard may be of 

 interest: (1) "Slender; the first cilia of the series 

 upon the process are somewhat but not remarkably 

 longer and stronger than the rest ; when rolled up 

 the ciliated bacillar process forms more than one 

 turn of a spiral. Sheath, flask-shaped and horny. 

 Hitherto found only in the open cells of torn leaves 

 of Lemna triscula, growing in fresh water near 

 Berlin." (2) " Choetospira, a new genus instituted 

 by Lachmann, has a ciliary apparatus so abnormal 

 and peculiar that it would seem rather a representative 

 of another family than one of the Vorticellinte. The 

 anterior portion of the body is much elongated, and 

 supports a ciliated process, when fully extended, 

 straight and of a sword-shaped figure, fringed along 



