920 SUMMARY OF CURRENT RESEARCHES RELATING TO 



thin layer of gum is again dissolved by the water ; or the paraffin 

 sections are laid at once in the liquid gum solution and, fixed in their 

 proper place, adhere whilst drying Either modification has its 

 advantages and disadvantages. With extremely delicate and small 

 sections ( • 003 mm. thick), the dry slide is unconditionally the best ; 

 with thicker (-01 mm.) and larger sections the wet process gives the 

 best results. 



If only few and small sections are to be mounted the removal of 

 the paraffin after fixing is unnecessary ; the balsam dissolves it 

 entirely. But if 50 or 100 sections are wanted together, the paraffin 

 should be removed, before putting on the cover-glass, by benzine, and 

 before it is evaporated balsam is quickly added. 



After a while the gum is removed by washing from every part of 

 the slide outside the cover-glass. 



Mounting Minute Insects and Acari in Balsam.* — Mr. A. D. 

 Michael describes his process as follows : — He first kills the crea- 

 tures in hot water or spirit. Hard insects and Acari are best killed 

 in hot water which causes them to expand their legs, but water 

 rather injures minute flies, and spirit is better for them. Next 

 wash the objects thoroughly in spirit and clean with a badger's 

 hair, clean mechanically and by washing in spirit. Place the 

 object on a glass slip and arrange it with the hair, leave it in 

 spirit for such a time as experience suggests, tilt the slip so as to 

 drain off the spirit, but not to dry the object, which should never be 

 allowed to dry from the first process to the final mounting. Having 

 drained otf the spirit, drop on the object a little oil of cloves, which 

 is better than turpentine ; slightly warm the slide and put on a thin 

 cover-glass, which must be supported so as not to touch the object ; 

 leave it until thoroughly soaked. If necessary remove to a clean slip 

 for the final mount. It may be necessary to arrange the object more 

 than once. Drain off the oil of cloves and put on a small quantity of 

 Canada balsam, or preferably balsam and benzole. Arrange the 

 creature on the centre of the slide. Let the balsam harden a little, 

 then the object will not float off, as happens sometimes when a 

 quantity of balsam is used at once. Lower the cover straight down 

 on the object ; do not try to drive out a wave of balsam as is recom- 

 mended in the text-books. It is better not to put enough balsam at 

 first to fill the space under the cover, as the balsam supports the 

 cover if it does not reach the edge, but if the balsam reaches the edge 

 of the cover it is apt to draw down the cover and crush delicate 

 objects. A few pieces of thin glass to support the cover are a great 

 protection to the object, or better still, a few tiny glass beads. 

 Finish the slide with a ring. Bell's cement or something of the 

 kind, but that must not be done unless the cover be supported in 

 some way. 



Collecting together Scales of Insects and other Minute Objects 

 upon one place on a Slide-t — G. Dimmock puts the scales in a drop 



* Journ. Quck. Micr. Club, i. (1883) pp. 241-2. 

 t Priyche, iv. (1883) p. 71. 



