CYTOLOGY OF THE MYXOMYCETES. 73 



I have found that formalin in 5 per cent, or 10 per cent, solution 

 preserves the normal form of mitochondria better than higher 

 concentrations. The subsequent long mordanting in potassium 

 bichromate may sometimes be omitted with equally satisfactory 

 results. 



Other mitochondrial fixatives have been devised containing 

 chromic, picric or osmic acid in varying concentrations. These 

 are the Benda, Champy and Regaud II and III which give very 

 good results, but mitochondria are, I believe, more constant in 

 their response to the Regaud mixtures given above. 



Sections should be cut about 3 or 4 /i in thickness. 



Staining: 



The Heidenhain Iron Hematoxylin Method: 



1. 5 per cent, iron alum, 24 hours. 



2. Wash in water, 5 minutes or less. 



3. i per cent, hematoxylin, 24 hours. 



(Made by dissolving 10 gm. hematoxylin in 100 c.c. of 

 absolute alcohol. This should be kept until ripe, 

 when IOG.C. of the mixture should be added to 90 c.c. 

 of distilled water.) 



4. Wash in water, 5 minutes. 



5. Differentiate in 2 per cent, iron alum under the micro- 



scope. 



6. Wash in water at least I hour. 



7. Pass through 50 per cent., 70 per cent, and 90 per cent, to 



absolute alcohol, clear in xylol and mount in balsam. 



The Bensley Method (E. V. Cowdry, 'i6b, p. 30} : 



1. i per cent, potassium permanganate, 30 seconds. 



2. 5 per cent, oxalic acid, 30 seconds. 



3. Rinse in water. 



4. Stain in Altmann's anilin fuchsin (anilin water 100 c.c., 



acid fuchsin 20 gm.), heat once until vapor arises, 6 

 minutes. 



5. Rinse quickly in distilled water. 



6. Differentiate in i per cent, aqueous solution of methyl 



green or toluidin blue very quickly. 



