PHYSIOLOGICAL CHARACTERISTICS OF AXIATE PATTERNS 91 



with extremely low concentrations all levels of the ectoplasm may reduce 

 the dye as rapidly as it enters; with slightly higher concentrations, the re- 

 duction gradient appears with rate of reduction decreasing from anterior 

 to posterior levels. The only alternative to this suggestion is apparently 

 a differential ability of the ectoplasm to decolorize the dye in some other 

 way than by reduction. 



In still higher dye concentrations the anterior ectoplasm becomes more 

 deeply stained than other parts, and reduction is retarded in it or does not 



Fig. 27, A-D. — Differential staining and differential reduction in Paramecium (methylene 

 blue). A, very low concentration, staining deepest parts of posterior entoplasm first; B, higher 

 concentration, stains posterior ectoplasm and with continued staining, injury, loss of struc- 

 ture and ability to reduce occur, progressing anteriorly while anterior region remains un- 

 stained; C, early stage of differential reduction after staining of whole ectoplasm; reduction 

 progresses from anterior end posteriorly; D, high concentration or long staining in high 

 oxygen; anterior ectoplasm stains more deeply than rest, and its reducing power is decreased 

 or destroyed, while posterior region still reduces (from Child, 19346). 



occur, while more posterior regions are still uninjured and able to reduce 

 (Fig. 27, Z)). When the leucobase of methylene blue prepared with hypo- 

 sulphite (see p. 68) is added to culture fluid containing Paramecium and 

 exposed to air, it penetrates at once and is almost immediately oxidized 

 in the animals. For a few seconds, however, an oxidation gradient appears, 

 rate of dye oxidation decreasing in the ectoplasm from anterior to poste- 

 rior levels; but staining very soon becomes uniform. Extremely high dye 

 concentrations, particularly of the leucobase with hyposulphite, are highly 

 irritating and induce long-continued backward locomotion. Under these 

 conditions the posterior ectoplasm oxidizes the leucobase and stains more 



