CONTRACTILE VACUOLES IN AMOEBAE— FACTORS IN- 

 FLUENCING THEIR FORMATION AND RATE OF 

 CONTRACTION 



By Mary Jane Hogue 



The presence of contractile vacuoles in protozoa, has long been 

 known. It is stated in most text-books that a contractile vacuole is 

 usually present in the fresh water protozoa and generally absent in 

 salt water protozoa. All the protozoan parasites in the intestine of 

 man are without contractile vacuoles and many protozoan parasites 

 in the intestines of other vertebrates are without them. This is espe- 

 cially interesting when one considers that the sodium chloride con- 

 tent of the digestive tract varies in the different vertebrates, but is 

 always much below that of sea water, which is often 3.04 per cent; 

 though this varies with the locality. 



Formation of Contractile Vacuoles 



While working at Woods Hole with Vahlkampfia calhensi, which 

 are parasitic in the digestive tract of the oyster and consequently 

 used to water of considerable sodium chloride content, I succeeded in 

 keeping them several days on agar medium made up with tap water 

 and with distilled water. These amoebae developed a contractile 

 vacuole similar to that of fresh water amoebae (Hogue 1). The ex- 

 periment was repeated many times and frequently the amoebae lived 

 five or six days on agar made up with fresh water. 



The following method was used : The amoebae were grown on 

 sterile agar made up with sea water or with 0.7 per cent sodium 

 chloride solution. Here they multiplied rapidly. From such a cul- 

 ture in Petri dishes, a small block covered with amoebae was cut out 

 and transferred to a Petri dish containing agar made up with dis- 

 tilled water. A small loop full of 0.7 per cent sodium chloride solution 

 was added to the transfer and seemed to facilitate the movement of 

 the amoebae and also to prevent the small block of agar from drying. 



At the end of 24 hours the amoebae were leaving the transplant 

 and wandering out onto the new medium, going only as far as the 



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