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 t!:e 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. JVlethyleue-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. 



