310 THE AMERICAN MONTHLY [Oct 



media. Bacteria-free cultures were never secured by this 

 method. 



In stained amoeba, the author states that the staining of 

 the nucleus is absolutely distinctive. Von Leyden com- 

 pares its appearance with that of a bird's eye. It con- 

 sists of a central spot (chromatin), surrounded by a 

 sharply defined, clear zone. This never occurs, says the 

 author, in a human or animal cell. Hence, by this fea- 

 ture alone, one can tell whether the object observed is a 

 body cell or an amoeba. 



For staining the amoeba found free in the culture fluid, 

 the author employed the following method: 



A drop of the fluid was placed upon a cover-glass and 

 a drop of serum added. On fixing with sublimate-alco- 

 hol, the albumin in the serum coagulated, and fixed the 

 amoeba in tlie state they were in at the moment. The prep- 

 aration, was then well washed with iodin-alcohol after the 

 method of Schaudien (Sitzbr. d. Acad. d. Wiss., 1896, 

 xxxix), stained for 24 hours in very dilute hematoxylin 

 solution, and sufficiently decolorized. In this method the 

 nucleus is more intensely stained than the protoplasm, 

 and is surrounded by a delicate, sharply-defined white 

 zone. Such a picture characterizes the amoeba as such. 



The encysted amoeba were treated as follows : 



Small particles of the organic substance which had 

 served the amoeba as a nutrient, were hardened in abso- 

 lute alcohol. They were next embedded in paraffin, and 

 cut in the ordinary way. Methylene-blue and eosin 

 were used for staining. The protoplasm also shows a 

 fine retiulate structure, which can be distinguished from 

 that seen in body cells by its more delicate meshes ; be- 

 sides, the reticulum noted by Flemming in human and 

 animal cells is not brought out by the methods of stain- 

 ing used by the author in these researches. 



