382 MR. WALTER WESCHE ON THE GENITALIA OF 



Chilled balsam. — Sometimes, in spite of care, tlie specimen, has not been sufficiently 

 dehydrated, and the balsam is " chilled " and the whole slide a failure, as nothing can be 

 clearly seen. The remedy requires careful nicety : — (1) Place a piece of white paper on 

 the hot-plate ; on the paper place the preparation. The paper prevents the glass 

 becoming too hot, and also shows the situation of the dissections, which often cannot be 

 seen without the white background. The balsam will soon melt, and the air will run 

 in ; (2) then lift off the upper glass with a fine pointed forceps, and place it balsam-side 

 uppermost on the paper. 



(N.B. — Do not use the forceps again till it has been dipped in spirit and the points 

 wiped. The neglect of this precaution has caused many disasters, and the flow of many 

 tears of the Recording Angel necessary for the obliteration of words *.) 



(3) Drop turpentine on the preparation ; this will drive all the balsam to the sides, 

 leaving the dissections in the middle, where the preparation can have a thorough 

 washing in evaporating turpentine repeatedly dropped on it. (4) Then put out the lamp 

 and proceed as before, dropping balsam, and sealing with the old or a fresh cover-glass. 



Sections.— li abundance of material is available, sections of the hypopygium can 

 be cut. 



Motmting without pressure. — There yet remains another method, but it cannot be 

 applied to insects larger than the house-fly, Musca domestica. This is the mounting of 

 the whole insect without pressure ; the initiatory processes are identical till it arrives at 

 the pressing stage. (5) Instead of being placed on a slip, it is placed in a small saucer 

 on its back and a little water poured in. The wings, legs, and proboscis are arranged in 

 their desired position. (6) The water is drawn off and replaced with spirit ; when the 

 specimen is quite stiff it may be lifted out with a section-lifter and placed in a closed 

 receptacle also filled with spirit, where it should remain for 48 hours or as much longer 

 as is convenient, to set thoroughly and dehydrate. (7) It is desirable that this receptacle 

 should have a flat bottom, as otherwise the arrangement of the insect will be altered 

 and possibly spoilt. (8) It is then lifted out very carefully, with the section-lifter as 

 before, and transferred to turpentine, but this must not be done till the operator is quite 

 satisfied that it is very thoroughly dehydrated, failures in this part of the process are 

 more likely in this type of mounting than in the pressure type. (9) After 48 hours in 

 the turpentine the insect can be lifted out and placed on a slide. (10) Cover it with 

 plenty of balsam and place round it (11) three or four glass beads of a suitable size (I 

 prefer transparent ones, zinc rings are equally good) ; these must have been prepared 

 (12) by being washed in alcohol and afterwards in turpentine. Transfer them straight 

 from the turpentine to the balsam, and their preparation will ensure that no air hangs 

 to them and that they sink readily into the thick medium. (13) Place a cover-glass on 

 the insect, M^hich will not be injured by the pressure as the cover-glass will rest on the 

 beads. (14) Put a weight (a small bullet answers well) on the cover-glass and then run 

 in balsam under it till it is quite fall ; this will shrink in a day owing to the evaporization 

 of the xylol ; (15) and fresh must then be run in till it is quite set and firm, when it 

 may be ringed in the usual manner. 



* Tristram Shandy : " And the lleoording Angel, as he wrote it down, blotted it out with a tear." — Stebne. 



