BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [14] 



Potassium bichromate, 5 per cent solution cubic centimeters.. 100 



Osmic acid, 1 per cent solution do 2 



Corrosive sublimate, saturated solution do 100 



Acetic acid, concentrated do 50 



Corrosive sublimate, saturated solution do 100 



Chromic acid of 1 per cent do 50 



Kleinenberg's solution : 



Picric acid, saturated solution do 100 



Concentrated sulphuric acid do 2 



Filter and add three times the volume of distilled water. 



Flemming's solution : 



Chromic acid of 1 per cent do 25 



Osmic acid of 1 per cent do 10 



Acetic acid (glacial) do 5 



Distilled water do 60 



Perenyi's solution : 



Nitric acid of 10 per cent do 40 



Chromic acid of 4 per cent do 30 



Alcohol of 90 per cent do 30 



Miiller's sohitiou : 



Potassium bichromate grams . . 2 



Sodium sulphate do 1 



Distilled water cubic centimeters . . 100 



Formalin solution (standard) : * 



Commercial formalin 40 per cent do 10 



Water do 90 



METHODS OF PEEPARATION AND PEESEBVATION. 



PROTOZOA. 



Protozoa are so small for the most part as to be invisible to the 

 unaided eye, and their preparation therefore comes within the field 

 of the microscopist, for which reason only the larger species will be 

 mentioned here. Certain Gregarinas which occur as parasites in the 

 intestinal nucleus of Salpa maxima-africana are best preserved with 

 Kleinenberg's solution, where they may remain for about an hour before 

 they are transferred to weak alcohol. 



RADIOLARIA. 



Thalassicolla is well fixed in chromic acid of ^ of 1 per cent, where it 

 may remain about an hour and then be transferred gradually to alcohol 

 of 70 per cent. 



Aulacanthidse and Acanthometrae are placed directly in 50 per cent 

 alcohol, and after a few hours are transferred to that of 70 per cent. 

 Good preparations have also been made by dropping a few drops of 1 

 per cent osmic acid into the sea water containing the animals and then 

 transferring them to alcohol after washing them in fresh water. Excel- 

 lent microscopic preparations of some of these species of minute pelagic 

 organisms have been made by a treatment with a saturated solution of 

 corrosive sublimate. 



