18 



and, after the addition of each supply of water, allowed to settle ; when 

 moderately clean, they may be separated from the filamentous algse, 

 sphagnum and myriophyllum leaves, &c., among which they exist, by 

 washing and squeezing thi-ough coarse "cheese-cloth," a kind of canvas 

 having 22 to 24 threads per inch ; by this means a dark, flocculent mass is 

 obtained, rich in these organisms. A little of this may be placed in the 

 cell with some of the fluid, and well stirred, when the Desmids will sink 

 through the supernatant debris, which may be skimmed ofi" by a few rapid 

 and gentle touches with a small pipette tube. A clean cover glass is then 

 taken, the under-side breathed upon to make it " take " the fluid, excess of 

 which exudes, and is absorbed by a little blotting-paper. The cell is then 

 closed with shellac varnish, two or three thin coats of which are applied, 

 and the slide is then ready for finishing. This is effected by a varnish 

 possessing plenty of " body," three coats being applied over the shellac. 

 It is needless to say that the varnish must have no action on the shellac. 

 Unless the mounter is very expert, he should avoid the too-frequently 

 recommended gold-size as either a cement or varnish, as it is rarely good 

 in quality, and when not good is unsafe. Zinc white and dammar is a 

 favourite finishing varnish, but the best one is asphalte-black varnish 

 mixed with a little (10 to 15 per cent.) of India-rubber dissolved in 

 turpentine. Finishing varnishes should be strained through a finely-woven, 

 clean, and dry piece of linen, before use. With care, slides thus prepared 

 ■will last for many years ; e.g., Mr. Turner now possesses slides, in good 

 condition, mounted by the late Henry Webb, of Birmingham, so 

 far back as 1850. Most micro-students seem to avoid fluid mounts ; 

 but they will, on trial, be found easy of production, and with a little 

 care will last a lifetime. If the study of these organisms is under- 

 taken, a few dozen cells of different sizes (those taking tV and ^ inch 

 covers are the most useful), should be kept in readiness for use as 

 required. 



At the close of W. B. Turner's lecture, the President (H. Bendelack 

 Hewetson, M.E.C.S.), expressed the gratification which he and other 

 members present had experienced in listening to it ; and there was a 

 discussion, in which several members took part. 



Several specimens were then shown. J. W. Addyman showed a 

 caterpillar of the Goat Moth (Cossics cossus), which had been sent to him 

 from Wimbledon, where a poplar tree infested with these destructive 

 creatures had recently been felled. J. W. Dixon showed various 

 marine shells from Margate, the most noticeable of which was the 

 European cowry {Cyprma eicropcea), the only British representative of a 

 family, whose genera and species abound in tropical and sub-tropical seas. 

 W. J. Fletcher had local specimens of shells, including Cochlicopa 

 luhrica, from Woodhouse Hill, Hunslet ; Zonites nitidulus, &c. ; 

 and W. E. Collinge a specimen of Anodonta utiatina, from Brentford, 

 Middlesex. 



