110 SAKYO KANDA. 



Then the writer made many small tubes for haematocrit attach- 

 ment, of about 4.7 cm. long and 0.3 cm. in diameter, inside meas- 

 ure. One end of each tube was sealed. One of these tubes was 

 filled with the gum-arabic solution mentioned above and the 

 number of drops which were put in the tube was counted. Now, 

 to the number of the drops of the solution, one drop of water was 

 added. Thus the difference of the specific gravity of the solution 

 before and after the addition of one drop of the latter to the num- 

 ber of drops of the former could be estimated. The writer thus 

 found that the addition of only one small drop of water to the 

 gum-arabic solution of the known specific gravity, that is, 1.0426, 

 lowered the latter to 1.0415. And when another drop of water 

 was added to this, it became about 1.0404. The addition of one 

 drop of water, therefore, lowered the specific gravity of gum- 

 arabic solution about o.oon. 



A pair of tubes was thus prepared with a definite number of 

 drops of the gum-arabic solution of the specific gravity 1.0415. 

 This pair was centrifuged as usual. Then on the top of the solu- 

 tion of one tube, one drop, and on the other, two drops of water 

 containing dense Paramecia were added. The tubes were again 

 centrifuged for two minutes with a speed of about 7,300 revolu- 

 tions per minute. The results were determined by means of a 

 magnifying glass immediately after the centrifugalization. All 

 the procedure was the same as the writer described in his pre- 

 vious paper. Thus the nearest possible density of the animal 



was obtained: 



TABLE I. 



Tube i. Dens, of gum-arab. sol. 1.0404. 

 I. All stay at upper part. 



Tube 2. Dens, of gum-arab. sol. 1.0393. 

 Majority stay near middle. 



Tube i. Dens, of gum-arab. sol. 1.0382. 

 II. Many stay at middle. 



Tube 2. Dens, of gum-arab. sol. 1.0371. 

 A few go to bottom. 



This was carefully tried with different cultures and no practical 

 difference was found. The writer, therefore, concludes that the 

 specific gravity of Paramecium caudatum is between 1.0382 and 

 1.0393- 



