732 SUMMARY OF CURRENT RESEARCHES RELATING TO 



sive alcohols was employed for fixing. A modification of Mayer's 

 hjemalum was found to be superior to lieematoxylin and other hasinatin 

 stains, both for sections and specimens in toto. For the latter Mayer's 

 haemalum diluted with 20 parts of ammonia alum was used. The 

 specimen was decolorised in 1-10 of 1 p.c. hydrochloric acid in 70 p.c. 

 alcohol. Alcoholic cochineal gave good results in toto. Benzo-purpurin 

 was advantageous in older stages. Orange G- was used as a plasma 

 stain on sections. The preparations were cleared in anilin or clove-oil, 

 and afterwards in xylol. 



Owing to the radially symmetrical appearance of the embryonic area 

 in the earliest stages, they were difficult to orient. They were imbedded 

 in celloidin, and then the celloidin was pared down until the embryos 

 could be observed under a low power. 



Triangular blocks were then cut with definite relation to the anterior 

 and posterior ends of the blastoderm. They were then re-imbedded. 

 The celloidin also acted advantageously in protecting the delicate 

 embryos which had become brittle after several years in alcohol. 



Demonstrating the Genitalia of Diptera.* — W. Wesche immersed 

 newly killed insects in 15 p.c. caustic potash. When all but the mem- 

 branes, the exoskeleton and the chitinous structures are dissolved, the 

 preparations are thoroughly washed in water, and then placed in glacial 

 acetic acid for 24 hours. They are again washed with water and then 

 arranged on slides. Another slide is superimposed, and the two com- 

 pressed by means of clips at both ends. If the arrangement is satisfactory 

 the slides are tied at the ends with twine, the clips removed, and then 

 immersed in methylated spirit for at least 24 hours. The preparation 

 may, if desired, be now stained, for which purpose anilin-blue is recom- 

 mended. It is now ready for transference to oil of turpentine : the 

 slides are carefully removed, and then the object is removed with a 

 section-lifter to turpentine, wherein it remains for at least 24 hours. 

 After this it may be mounted in balsam, though some preparations are 

 better for a further clearing in oil of cloves. Examination of the pre- 

 parations should be made with a medium power (j-) aided by a substage 

 condenser. 



For dissecting under the Microscope, the end of the abdomen must 

 be removed and placed in a drop of water in a live-box or compressorium 

 (the cover being removed), and the organs teased apart by fine needles. 

 The forcipes must be separated from their articulated bases, and the penis 

 and appendages brought out free from the adhering muscles and duct. 

 Impose a cover-glass and examine. Next take a -§- in. cover-glass, place on it 

 a small drop of spirit, and then, by means of a bristle or needle, the parts. 

 Examine with lens, and, if the arrangement be successful, place some 

 more spirit on the cover-glass and put it on a piece of white paper and 

 both on the hot-plate, which must then be gradually heated. As the spirit 

 evaporates it must be replaced with fresh ; a glass needle answers best 

 for this purpose. When dehydrated, the preparation is treated with 

 turpentine, and when cleared is mounted in balsam by superimposing 

 another and thinner cover-glass. This f- in. glass when dry can be mounted 



* Trans. Linnean Soc. (Zool.), ix. (1906) pp. 339-86 (136 figs.). 



