1899] MICROSCOPICAL JOURNAL. 165 



may be seen by adding- weak acids or weak alkalis to such 

 a watery solution of it as can be made — acids turning- the 

 solution blue and alkalies changing it to a pink, the stain 

 acting as a delicate indicator. The same result comes from 

 heating such weak watery solutions which turn blue on 

 warming but turn back to the original color on cooling. 



Cover-glass preparations are made in the ordinary way 

 except that the glasses must be absolutely clean and free 

 from acid or alkalis, and on them as soon as the extremely 

 thin films are dry a few drops of the staining solution is to 

 be poured, no previous fixation being required. Keep the 

 supply of clean cover-glasses in absolute alcohol. Cover 

 the specimen with a watch glass to prevent evaporation 

 and consequent precipitation. In from one to three min- 

 utes, the stain should be poured off, the specimen rinsed in 

 distilled water if possible till the film has a pink color. 

 This will occur in 5 to 10 seconds. If filtered water is 

 not available, use other but immerse only momentarily and 

 dry between filter-paper or rapidly over flame. Dry it 

 high up over a flame or filter by agitation in the air. Mount 

 in xylol balsam. Under the microscope, the red discswill 

 be of a terra-cotta color ; the nuclei of the white corpus- 

 cles, blue ; the platelets, mauve ; the granules of the poly- 

 morphonuclear white cells and of myelocytes, red ; the 

 granules of the basophils (mast cells), dark violet ; bacte- 

 ria, filaria, or malarial parasites blue. If the specimen is 

 washed in unfiltered water, the red colors are more pro- 

 nounced ; the blue of the white cell nuclei will be almost 

 washed out while the dark blue of the smaller hyaline 

 white cells (lymphocytes) stand out in strong contrast to 

 the now pale nucleus. 



Multiple Images in the Cornea of a Beetle's Eye. — 

 In a large number of text-books on the microscope it is 

 stated that if the cornea of a beetle's eye be placed on the 

 stage of a microscope, and an object be placed between 

 the source of illumination and the cornea, that object will 

 be seen reproduced in every facet of the cornea. The ex- 

 periment is an exceedingly interesting one, but there are 



