BASED ON A STDDT OF THE MALE GENITAL ARMATURE. 13 



Methods of preparing the male genitalia for microscopical 

 examination. 



The specimens used in the preparation of this memoir were all in a perfectly 

 dry condition so that it was necessary to macerate them in order to be able to 

 turn the hypopygium back and display the various structures. The best method 

 is as follows : — 



1 . Either break off the abdomen close up to the thorax or clip it off with a 

 pair of scissors midway in the region of the third or fourth segment. It is best, 

 however, to leave as much of the abdomen attached as possible so as to facilitate 

 the final mounting of the preparation. The armature can also be dissected out 

 with a fine scalpel, but the result is not nearly so satisfactory ; though this method 

 may be adopted in the case of rare and valuable sjiecimeus. 



2. Place the abdomen in a test tube and partly fill it with 10 per cent, caustic 

 potash (K O H). Write with a pencil on a slip of paper the full data and place 

 it in the upper portion of the tube, away from the liquid. Place the tube in a 

 water-hath and boil over a bunsen for fifteen minutes. 



3. Eemove from the potash and wash in clean water for five minutes. Then 

 take a No. 1 sable brush and roll it toicards the hypopygium until the latter is as 

 fully distended as possible ; repeat the process until all the dirty fluids (dissolved 

 body-fats, etc.) have been expelled. 



4. Immerse for five minutes in 50 percent, alcohol ; and for an equal time also 

 in absolute alcohol, taking care that the claspers are kept well distended. 



5. Immerse in clove oil for ten minutes, again displaying the claspers with the 

 brush. If the preparation has not cleared thoroughly it is a good plan to heat 

 the oil, which will remedy the defect immediately. 



6. Place the abdomen on a glass slide and with the larger species put two 

 small broken fragments of a cover-glass, one over the other on either side of it 

 in order to relieve the pressure of the cover-glass. With the smaller species 

 {morsitans, etc.) this method is not needed. 



Staining with Carbol Fuchsin brings out certain details very clearly ; but unless 

 the student has had previous experience in this method it is not advisable to 

 adopt it. 



All the members of the fusca group must be mounted so that the armature 

 may be studied in profile ; though a dorso-ventral position is necessary for the 

 determination of the width between the superior claspers. Members of the 

 groups II and III must be mounted in a dorso-ventral position, otherwise 

 the superior and also the inferior claspers will not show properly ; care must also 

 be taken to place all of these with the venter uppermost. The Canada balsam 

 should not be too thin and both the slide and cover-glass shoidd be warmed over 

 a bunsen or spirit lamp. 



The species belonging to groups I and III can be mounted with comparative 

 ease ; but those belonging to group II are somewhat difficult owing to the 

 tendency of the superior claspers to fold back over the hypopygium, but with 

 care they can be fully distended, and this is absolutely necessary, otherwise the 

 surrounding organs will not be properly displayed. In all cases where it is 

 necessary to mount the examples in profile the abdomen must be placed upon its 



