THE INTIMATE STRUCTURE OF THE CELL 189 



An example after this treatment is shown in Fig. 526". Some- 

 times this can be accompHshed merely by pressing the cover- 

 slip laterally downwards, sufficiently firmly to cause the cell 

 to become somewhat flattened out. The effect of iodine on 

 the cell is most marked, for it causes the outer plasma and its 

 attached cilium to swell up in a very irregular fashion, and if 

 the reagent be removed before it has affected the inner plasma 

 it is possible to distinguish between the inner and the outer 

 plasma with great clearness (Fig. 52 b and/). By allowing the 

 cells to remain in picric acid for two weeks and then staining 

 with dilute methylene blue the separation of the tw^o plasmas 

 may be made complete as is shown in Fig. 52t/. In this in- 



FiG. 52. — Chromatium Linsbatieri (Gicklhorn). x 1000. 



a. — Unstained individual showing a single siime area at one of the ends. 



b. — Cell treated with picric acid for two weeks, and then stained with dilute 

 methylene blue. The outer plasma is shown with the cilium in 

 attachment and the widely separated inner plasma has contracted 

 and resumed the rounded form natural to the organism. 



c. — Cell which has been treated to make a part of the inner plasma project 

 through the slime areas. 



d. — Cell treated with iodine, which causes irregular swelling of the outer 

 protoplast. The irregularity in the swelling is noticeable even in the 

 cilium. 



e.— Normal organism showing its single polar cilium and one slime area. 



/. — Cell in which the treatment with iodine has been advanced a step 

 further than is shown in [d). The inner plasma has begun to disin- 

 tegrate. The large irregular empty space marks the position of a 

 slime area. 



stance the outer plasma with its attached cilium has evidently 

 been destroyed by the acid, but the inner plasma, protected 

 probably by the slime layer, has not succumbed but has con- 

 tracted and rounded itself within the destroyed outer plasma. 

 It is noteworthy that when this takes place the contracted 

 inner plasma appears to be bounded by a cell membrane. 

 This effect is an optical one, as can be seen when the cell is 

 pressed flat. 



It is highly probable that the inner and outer protoplasts 

 are connected by plasma strands, otherwise the organism could 

 not function as a physiological unit. It is possible, however, 

 that the slime layer may in reality be a somewhat tenuous 



