478 SUMMARY OF CURRENT RESEARCHES RELATING TO 



resting on the upper points of the curves. By leaving an excess of 

 balsam round the cell and cover-glass, air-bubbles ultimately escape 

 through the spaces, and loss by evaporation of essential oil in the 

 balsam is provided for. If the cell is too deep for the object it can 

 be pressed between two glass slips until shallow enough. 



Closing Glycerine Cells. — Mr. W. M. Bale writes : " I see by one 



or two remarks in the Journal that some manipulators still find a 

 difficulty in securely closing glycerine cells. I have found the 

 following plan obviate all liability to leakage. Use a cell of firm 

 material, such as glass or ebonite, and a cover-glass of larger size, so 

 that when in position it projects outside the cell for 1/12 in. or 

 1/8 in. all round. Fill the cell and press down the cover-glass, 

 forcing out the superfluous glycerine ; then (if on examination under 

 the Microscope the object is found to be properly displayed) put on a 

 spring clip to keep the cover close down, and with a fine syringe 

 wash away the whole of the glycerine which may have exuded from 

 the cell. The space below the projecting margin of the cover-glass 

 will now be filled with water instead of glycerine, and by applying a 

 piece of blotting-paper the water may be absorbed ; the slide must 

 then be allowed to stand for a minute or two till the outside of the 

 cell is quite dry, when a little tenacious fluid cement may be applied 

 at the margin of the cover, and allowed to fill the circular space 

 outside the cell. Unless an excess of cement be placed on the 

 slide there will be no tendency whatever to ' run in,' provided that 

 the cell be quite flat, so that the cover can come into close contact 

 with it all round, and that it be deep enough for the object. I 

 formerly recommended this plan for mounting in fluids which would 

 evaporate,* and I since find that it is equally applicable to a dense 

 medium like glycerine, provided that the latter be syringed away 

 from the outside of the cell, as directed. I have young Hippocampi 

 preserved in ebonite cells in this manner, but I may add that it is 

 not uncommon to find ebonite cells more or less bent, and such are 

 useless for the purpose, it being essential that the cover should fit closely 

 to the cell, as otherwise the water used in washing would enter it." 



Getschmann's Arranged Diatoms. — Whether diatoms ought or 

 ought not to be "arranged" is a question which is more often 

 answered in the negative, and in calling attention to the slides pre- 

 pared by E. Getschmann of Berlin, we have no intention of objecting 

 to the general verdict. We simply record the fact of the existence of 

 the slides, and that they much surpass any of the previous efforts with 

 which we are acquainted. With the diatoms are included Lepidoptera 

 scales, Echinoderm spines, &c. 



Classification of Slides.! — Dr. C. S. Minot suggests a scheme of 

 arrangement of microscopical (and especially histological) slides 

 based on embryology. The foundation of the system is primarily 

 the germ-layers and then the order of development of the various 

 organs. 



* See this Journal, iii. (1880) p. 864. 

 t ' Science Kecord,' ii. (1884) p. 65. 



