THE GEOTROPISM OF PARAMECIUM CAUDATUM. IO9 



of the centrifugal force upon the protoplasmic materials of the 

 organisms." 1 



While the writer was conducting experiments with a vital stain 

 method in the physiological laboratory of the University of 

 Minnesota, and after he had obtained some valuable results, he 

 learned that McClendon had already published satisfactory re- 

 sults in 1909. 2 The writer found that McClendon's method 

 showed better results than those obtained with vital stains and 

 has, therefore, adopted that method for this investigation- 

 although not able to agree with all of McClendon's interpreta- 

 tions. 



This paper attempts to show that Paramecium caudatum con- 

 tains protoplasmic substances of different specific gravities, and 

 subjects to further experimental examination the various phe- 

 nomena of geotropism in the animal, described by various inves- 

 tigators. The expeiimental work was done during the academic 

 year of 1913-1914, while the writer was holding a Shevlin Fellow- 

 ship in the medical school of the University of Minnesota. 



II. MATERIAL. 



A dense culture raised in hay infusion from a single individual 



was used. 



III. EXPERIMENTAL. 



i. The Specific Gravity of Paramecium caudatum. 



As to the difference of the specific gravity of the Paramecium 

 between Lyon's 1.048 or 1.049 an d the writer's 1.037 or l -37 

 0.003, the latter suggested 3 a possible source of error in Lyon's 

 experiments. The w r riter this time examined the subject more 

 carefully. 



He prepared a gum-arabic solution using distilled water, as 

 in the case of his previous experiments. He dialyzed the neutral 

 solution through parchment paper. The specific gravity of the 

 solution so prepared was determined by means of a U-shaped 

 picnpmeter, as 1.0426. 



1 Kanda, Sakyo, 1914, "On the Geotropism of Paramecium and Spirostoniiw," 

 BIOL. BULL., Vol. 26, p. 22. 



2 McClendon, J. F., 1909, "Protozoan Studies," Jour. Ex. Zool., Vol. 6. 



3 Kanda, Sakyo, loc. cit. 



