H. MUNRO FOX 497 



The following is an account of four experiments which illustrate 

 this point. The same Bodo culture was used throughout. In each 

 experiment two preparations were made; {a) with Bodo suspension 

 taken straight from the culture jar, and {b) with a suspension pre- 

 viously aerated. In Experiment 1 the aeration was done by pouring 

 from one watch-glass to another for 15 seconds. The times taken 

 for the band of flagellates to take up its stationary position were; 

 {a) 11 minutes, and {h) 45 minutes. In Experiment 2 the aeration 

 was done in the same way and the times were; (a) 4 minutes, and {h) 

 46 minutes. In Experiment 3 the aeration was performed by leaving 

 a small quantity of the liquid in a watch-glass for 56 minutes at 18°C., 

 the laboratory temperature being 23°C. The times were; (a) 2 

 minutes, and {b) 56 minutes. In Experiment 4 for the preparation 

 of Slide (a) 10 cc. of Bodo suspension were kept in a watch-glass for 

 ^ hour at 26° and for {b) 10 cc. were similarly treated at 17°. There 

 was no noticeable difference in activity of the flagellates at the two 

 temperatures. As soon as the liquids were pipetted under the cover- 

 glasses their temperatures became identical and equal to that of the 

 laboratory so that the different times taken for the bands to become 

 established must have been due to the different quantities of oxygen 

 which had gone into solution at the two temperatures. The times 

 were; (a) 2\ minutes, and {b) 14 minutes. 



The consumption of oxygen in the center of developing Bodo rings 

 can be demonstrated in preparations containing hemoglobin. For 

 this purpose a pipetteful of liquid from a Bodo culture is placed in a 

 watch-glass and one or two drops of blood from a pricked finger are 

 mixed with it. The blood becomes laked. It in no way interferes 

 with the activity of the flagellates. If now a preparation is made 

 in the usual way beneath a supported cover-slip, no sooner does the 

 central aggregation of flagellates become a ring than the bluish color 

 of the region surrounded by the ring shows that it contains reduced 

 hemoglobin. The blue color here is in marked contrast to the scarlet 

 of the oxyhemoglobin outside the ring of flagellates, and the distri- 

 bution of hemoglobin and oxyhemoglobin is easily verified with the 

 microspectroscope. Thus after the flagellates have used up the avail- 

 able free oxygen dissolved in the water, they extract that which is 

 bound in the oxyhemoglobin. When this too is exhausted at the 



