568 MARY J. HOGUE 



cent medium is not sufficient for the great growth and multi- 

 plication of the bacteria. 



The amoebae grown on the 1, 1.5, and 2 per cent agar media 

 show shght differences in the form and shape of their pseudo- 

 podia. Those grown on the 1 per cent agar are similar to those 

 grown on the 0.5 per cent agar, and those on the 2 per cent agar 

 are similar to those grown on the 2.5 per cent agar. 



On the 1 per cent agar the amoebae multiplied very slowly 

 and spread out rather evenly over the Petri dishes but soon 

 encysted. Figure 4 shows some amoebae from a week old cul- 

 ture. The pseudopodia are irregular and the animals slightly 

 elongated. This medium was not well suited to the growth of 

 the amoebae. 



In figure 5 the amoebae had been one week on the 1.5 per cent 

 agar. The pseudopodia, when present, are very small, irregu- 

 lar protrusions of the ectoplasm. The amoebae are of good size. 

 This is an excellent medium for their growth and multipUcation. 

 The 2 per cent medium is an equally good one for their growth. 

 Both here and on the 1.5 per cent agar the bacteria do not mul- 

 tiply more rapidly than the amoebae. In other words the food 

 supply and demand seem to be more evenly balanced. Figure 

 6 shows amoebae grown on the 2 per cent medium. The pseudo- 



Fig. 1 Amoebae drawn from a 2.5 per cent agar medium, two days old. 



Fig. 2 Amoebae drawn from a 0.5 per cent medium of agar. Two days old. 

 Surrounded by bacteria. 



Fig. 3 Amoebae from a seven day old 0.5 per cent agar culture. 



Fig. 4 Amoebae from a seven day old 1 per cent agar medium. 



Fig. 5 Amoebae from a 1.5 per cent agar medium. A, b, and c, were sur- 

 rounded by bacteria. D and e were beyond the bacterial zone. F had a few- 

 bacteria around it. 



Fig. 6 Amoebae from a seven day old 2 per cent agar medium. A, b, and c 

 had a few bacteria around them. D and / were beyond the bacteria. E was 

 surrounded by bacteria. 



Fig. 7 Drawings made of amoebae soon after they were transferred from 1.5 

 per cent agar medium to water. 



Fig. 8 Amoebae surrounded by bacteria. From an old culture. 



Fig. 9 A and b are amoebae from the center of an old culture, showing the 

 small size of the amoebae in these cultures. C, d, and e are from the edge of the 

 culture. 



