oj Natural History fur the Microscope. 2 43 



These are made by merely painting the glass slider with a thin 

 eoatiug of varnish so as to leave an empty elear spaee of the size 

 desired. These will be ready for use in twenty- four hours. If time 

 is an object, they may be placed on the fire " hob/' and in a quarter 

 of an hour your cell will be ready for use. If a thick cell be re- 

 qiured, a second or third coating should be a])j)lied : it is far better 

 to make deep cells by three or fom* coatings, letting the preceding 

 one be quite dry, than to form it at once by a single thick aj)pli- 

 cation of the varnish. And now with regard to the fluid for ])re- 

 serving the objects in, ^Ir. Berkeley and Br. GrifKth recommend 

 Goadby's solution. This docs very well for animal substances, 

 but is totally inadmissible, so far as my experience goes, in a very 

 great number of vegetables. The endochrome of the Zygnema is 

 coagulated by it, and the beautiful spiral in the interior of the 

 cell is destroyed, and the same has been the case in other delicate 

 confervoids where I have tried it ; in place of the bright green 

 in many of these, they have presented a dull leaden appearance. 

 Pollen tubes mounted in it are invariably spoiled. This obtains 

 equally where spirit of wine is made use of, even though used in 

 a very dilute state ; it has also the additional disadvantage of cor- 

 rugating and making opake. 



The fluid 1 make use of is simply cold water ; perhaps it would 

 be better if pre^ iously boiled and allowed to stand for a short 

 time : filtering in my opinion should never be had recourse to 

 with any fluid used for microscopical pui-poses, as the liquid in 

 passing through the bibidous paper will always carry ^^^th it small 

 flocci from the paper, and the presence of these materially inter- 

 fere with the beauty and perfection of the object to be viewed. 

 AVhen the object is varnished donni and all contact ^\'ith the at- 

 mosphere is cut off, it is impossible that decomposition can take 

 place. In the case of marine Algre I make use of salt water which 

 has been allowed to stand for some little time in order that all 

 the impurities may subside. Many hundred objects have been 

 mounted by me in the manner described, which are as perfect 

 in every respect as they were on the day in which they were first 

 prepared, in shape, colour, &c. : probal)ly the most delicate pre- 

 paration I possess is a slider of the cells of the anther of Char a 

 hispida, in which the spermatozoa are beautifully shown, some in 

 the cells, others in the act of quitting the cell, and some spread 

 over the surface of the glass in the cell. Now if decomposition 

 did take place in this method of mounting, it would doubtless 

 have attacked and destroyed long before this these delicate little 

 animalcules, animal matter being much more liable to the de- 

 structive process, cceteris paribus, than vegetable. ?Janv months 

 have elapsed since they were mounted (in ]\Iay last). 



Every working microscopist examines with the object immersed 



