IO SAKYO KANDA. 



so prepared were put in a tube as described in the preceding 

 experiments; the tube was already filled between the points be 

 with about 0.2 c.c. of distilled water. The tube then was cen- 

 trifuged. The procedure was exactly the same as the preceding 

 experiment. In this case, every animal was found with its 

 posterior end unmistakably directed toward the open outer end 

 of the capillary tube. From the presence of the ingested iron 

 in the posterior end of the animals, we should expect this end 

 to be heavier than the anterior end, as Harper says. It is no 

 wonder then that the "heavier posterior end" in this case was 

 passively thrown away from the axis of the centrifuge, as the 

 heavier anterior end was in the normal case. This is the only 

 possible conclusion we can draw. Lyon's view in this respect is 

 fully confirmed, and Harper's explanation is not satisfactory. 



Experiment c. The writer repeated Harper's experiments on 

 the paramecia which had ingested iron as already described. 

 He placed one control tube containing a thick culture of normal 

 paramecia, side by side with a series of five tubes, a to e, con- 

 taining iron-ingested animals which were exposed to the iron- 

 containing medium for different periods, as follows: a for 30-40 

 seconds, b for two minutes, c for 3.30 minutes, d for 5 minutes, 

 and e for 10 minutes. All of the tubes were in a vertical position. 

 About 1 8 minutes later, in the control tube, about 70 per cent, of 

 the animals had gathered at the top, 20 per cent, at the bottom, 

 and the rest were scattered through the tube. In all the treated 

 tubes, about 80 per cent, of the animals had gathered at the top 

 and the rest were scattered through the tubes; except in tubes 

 a and b where there was on the bottom of each tube a small 

 dense gathering which disappeared about 10 minutes later. 

 After about two hours and fifty minutes, in all treated tubes, 

 almost all the animals had gathered at the top, especially in 

 tube e, and a very few were scattered here and there, while in the 

 control, 70 per cent, were still at the top and the rest at the 

 bottom. 



According to Harper, the ingested iron "particles are at first 

 lodged in the posterior end," and "the changed response is 

 coincident with this condition and tends to disappear as the 

 particles become more evenly distributed through the endo- 



