1913.] 



Colpoda cucullus from its Resting Cysts. 



431 



Formalin : 40-per-cent. formalin does not dissolve either ectocyst or 

 endocyst in the cold. Prowazek* mentions that Kutscher found paramylum 

 was soluble in formalin. 



Protein Tests. — Xanthoproteic test : cultures containing ectocysts and endo- 

 cysts were carefully heated with concentrated nitric acid and then ammonia 

 was added, but no coloration resulted. Millon's reagent was used on two or 

 three occasions, but there was no red coloration of the cyst-membranes, 

 though by this method protein was detected in the protoplasm of Colpoda by 

 the brick-red coloration. 



Starch and Cellulose Tests. — Iodine in potassium iodide solution does not 

 stain ectocysts or endocysts, though it passes through the latter very readily 

 and stains the Colpoda, light brown. Preparations treated with iodine are not 

 affected when strong sulphuric acid is added. Ammoniacal cupric hydrate 

 does not dissolve either ectocyst or endocyst. Corallin soda solution does not 

 stain the endocyst pink. These negative reactions show that the cyst- 

 membranes are not composed of starch or cellulose. 



The following carbohydrates occur in certain protozoa : — 



Glycogen^ has been observed in a number of ciliated protozoa, Opalina, 

 Paramecium, and Vorticella. It stains light or reddish brown with iodine. 



Paraglycogen| occurs as refractive spherules in certain of the Sporozoa. 

 With iodine it stains brown, which changes to wine-red or violet on the 

 addition of 70 per cent, sulphuric acid. It is soluble in hot water. 



Paramylum§ is a carbohydrate nearly related to cellulose. As prepared 

 from Euglena viridis by Butschli it did not stain with iodine in potassium 

 iodide solution nor was it affected by the addition of 70-per-cent. sulphuric 

 acid. It is insoluble in cold and hot water and is hydrolysed by continued 

 boiling with strong sulphuric acid. 



It is evident that the cyst membranes of Colpoda, are not composed of 

 glycogen or paraglycogen. They resemble paramylum in their reactions to 

 iodine and in the fact that the endocyst disappears on being heated up with 

 acid. It will be shown later on, however, that they are not composed of 

 paramylum. 



Reactions to Stains. — The following substances were tried in order to 

 determine what staining reactions are given by the cyst-membranes : — 

 Picric acid, a strong aqueous solution : membranes not stained. 



* Prowazek, S. von, ' Einfiihrung in die Physiologie der Einzelligen (Protozoen),' Berlin, 

 1910, p. 13. 



+ Prowazek, S. von, loc. cit. ; Butschli, C, loc. cit., pp. 1469-72. 



% Butschli, O., loc. cit., pp. 1469-72 ; Minchin, E. A., "The Sporozoa," 'A Treatise on 

 Zoology,' Pt. 1, 2nd Eas., 1903, p. 182. 



§ Butschli, 0., " Kenntniss des Paranrylons," ' Arch, fiir Protist.,' 1906, vol. 7, p. 199. 



