THE PERMEABILITY OF CELLS 525 



these minute granules take the dye and at the same time fuse 

 together to form clearly defined red bodies much like the chroma- 

 phores of Arbacia eggs. The final stage is more rapidly attained 

 in eggs with fertilization or artificial membranes. Inasmuch as 

 the conditions under which the dye unites with the granules in 

 the two types of eggs, fertilized and unfertilized, may be different, 

 we cannot at present draw conclusions as to differences in per- 

 meability to dyes in the two types of eggs. 



In brief the mechanism of staining Paramoecium or marine 

 eggs is as follows : The dye enters the egg as the weak base, yel- 

 low in color, and combines with a specific insoluble substance 

 present, in the form of granules. The combination resulting, like- 

 wise insoluble and comparable to a salt, is red in color just as are 

 the water soluble salts of neutral red. The exact chemical nature 

 of the granules with which neutral red combines is unknown. 



THE PENETRATION OF ALKALIES 

 1. Method and previous results 



Of the many methods which may be used in studying the pene- 

 tration of various substances, the color change of an indicator 

 within the cell is the simplest and most delicate for the detection 

 of acids and alkalies. Many plant cells contain natural pig- 

 ments which may serve as indicators. Both Pfeffer and DeVries 

 made use of such pigments in their studies on permeability. 



DeVries (71, p. 24) noted that the red sap of beet cells becomes 

 brown to yellow brown in dilute NH4OH and the red color comes 

 back again on washing in pure water. 



Pfeffer (77, p. 140) showed that the red sap of Pulmonaria 

 petals and of the stamen hairs of Tradescantia becomes first blue 

 then greenish in dilute ammonia. KOH and K2CO3 act like ammonia 

 (p. 141). Pfeffer regards the dead and the living plasma to be 

 similarly easily permeable for dilute alkalies as well as acids. 

 This is the view stated in botanical text-books at the present day 

 and the subject is dismissed with few words and without further 



THE JOURNAL OF EXPERIMENTAL ZOOLOQy, VOL. 10, NO. 4 



