ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 883 



3. Soaked for a short time in a very thin solution of gum arabic 



then in a somewhat thicker solution, and finally imbedded 

 in a very thick solution. 



4. Hardened in 90 per cent, alcohol. 



5. Thick sections prepared for dissection with needles. The 



sections are placed on a slide in water, which dissolves the 

 gum. 



Flemming's further Method for Staining Nuclei.* — In his 

 recent researches on karyokinesis, W. Flemming 6tates that he 

 obtained serviceable staining of nuclei in the following ways : — 



1. Living eggs of Echinoderms coloured on the slide, either with 

 safranin or aniline dyes, followed by acetic acid (1 per cent.) which 

 is allowed to flow under the cover and thus replace the staining 

 medium, or with acetic acid carmine (after Schneider), used undiluted. 

 The last mentioned staining agent causes swelling, but still gives the 

 typical features of the karyokinetic figures. 



2. Eggs first hardened in strong nitric acid (40-50 to aq. dest. 

 60—50), then washed in distilled water until the yellowish colour, due 

 to the presence of the acid, disappears. Coloured with acetic acid 

 carmine. 



Iodine-green and Methyl-green t — Dr. M. Flesch calls further 

 attention to the suitability of the combination of the green with red 

 staining matters. He has excellent preparations of cartilage, skin, 

 and glands hardened in Muller's fluid and alcohol, and stained with 

 methyl-green, and afterwards with picrocarmine. If the colour is 

 not so beautiful as in the case of objects stained with carmine and 

 hematoxylin, it is nevertheless very useful, as it is, he believes, easy 

 to preserve, and moreover it gives very sharp differentiations. 



Dr. Flesch uses an aqueous solution of commercial methyl-green 

 diluted until the section in a watch-glass is still recognizable on a 

 bright ground. 



Preparation of Epidermis. £ — W. Pfitzner prepares the epidermis 

 of tadpoles by first hardening in chromic acid, and making fine 

 sections with the Thoma microtome of a piece as free as possible 

 from pigment, imbedded in elder pith ; the best thickness for the 

 sections is '01 to "015 mm. The sections are washed for at least 

 thirty minutes in distilled water to remove the chromic acid. 



Pfitzner has three methods of mounting, either of which may be 

 employed, with various modifications : — 



1. Staining, a. With saffranin, mount in dammar, b. With 

 hematoxylin, mount in dammar ; or, c. As o, but mount in glycerine. 



2. Gold treatment : — Treatment with 1 per cent, solution of gold 

 chloride, with a trace of hydrochloric acid, for 15 to 30 minutes, in 

 the dark ; the sections are then carefully washed and exposed to 

 daylight for 12 to 24 hours in a 5 per cent, solution of formic acid, 



* Arch. f. Mikr. Anat., xx. (1881) p. 1. Cf. Amer. Natural., xvi. (1S82) 

 p. 780. See also Flemming's earlier method, ante, p. 715. 

 t Zool. Anzeig., v. (1882) pp. 554-5. 

 X Morpholog. Jahrb., vii. (1882) pp. 731-2. See also ante, p. 871. 



