50 Journal of the Mitchell Society [August 



bacteria, which served as their food, had spread. The following days 

 they wandered still further from the transj)lant but were always 

 within the zone of bacterial growth. Food vacuoles were present and 

 a contractile vacuole appeared and pulsated. Pseudopodia were form- 

 ing and the animals were moving about slowly. 



Slides were made from these cultures. Many amoebae were put 

 on a slide. They were fixed with Schaudinns solution and stained 

 with iron haematoxylin in the usual way (Hogue 1), but with very 

 different results. Many of these amoebae did not stick to the slide, so 

 that only a few were finally stained and mounted. The amoebae 

 seemed to have lost their power of adhesion when they were trans- 

 ferred from a salt water medium to a fresh water medium. 



This is interesting when one compares it with Zuelzer's (2) results. 

 The two experiments are the reverse of one another. She took 

 Amoeha verucossa from fresh water to sea water and found that in its 

 new medium it lost its power of adhesion. This loss of power of ad- 

 hesion must be due to some change in the physiological condition of 

 the amoeba due to the change from a medium of one salt content to 

 that of another salt content. 



In another respect the two amoebae, in their new media are similar. 

 Vahlkampfia calkensi seemed to feed. It had food vacuoles full of 

 bacteria. Amoeba verucossa also had vacuoles containing partly di- 

 gested food. 



On the other hand, Amoeha verucossa in salt water did not form 

 pseudopodia and did not move forward. It rolled around but did not 

 cling to the glass, whereas Vahlkampfia calkensia formed pseudopodia 

 and moved out over the new medium. 



Amoeha verucossa in salt water lost its contractile vacuole M'hile 

 Vahlkampfia calkensi in fresh water formed a contractile vacuole. 

 Neither amoeba reproduced in its new environment. 



When we consider that one function of a contractile vacuole is to 

 regulate the osmotic pressure of the protoplasm it is to be expected 

 that a contractile vacuole will be formed and function when the 

 amoebae are taken from a medium with high sodium chloride content 

 to one free from sodium chloride. 



