36 ACTION OF AUXETICS AND KINETICS 



and as the amoebae were not degenerate, we see no 

 reason for attributing it to plastogamic fusion. At 

 the same time, we have no direct evidence of any 

 sexual changes being involved. 



THE ACTION OF ALKALIES AND ACIDS 

 ON AMOEBAE 



Alkalies. Free amoebae placed on a jelly con- 

 taining O'l per cent, sodium bicarbonate show 

 diminished movements, and their general body 

 form becomes more rounded, but they are not 

 killed. With 0'5-per-cent. NaHCO 3 , the amoeba 

 exhibits a perfectly circular contour, and the 

 ectoplasm bulges out as the amoeba dies and lique- 

 faction of the cytoplasm takes place. With 1 -per- 

 cent. NaHCO s , the amoeba dies almost instantly, 

 and swells and bursts before it can be properly 

 examined. By cultivation on alkaline media so 

 strong as partially to inhibit bacterial growth, very 

 minute forms appeared which persisted in this 

 condition and ultimately formed small cysts. It 

 has often been noticed that amoebae on alkaline 

 jellies assume a more rounded type of form, while 

 on acid media they tend to become lengthened 

 out ; the significance of this is unknown. Alkalies 

 hasten the diffusion of stains into living amoebae or 

 their cysts. 



The cysts are very tolerant to alkalies and are 

 thereby rendered more resistant ; after exposure 

 to 5-per-cent. caustic soda or ammonia vapour 

 for twenty-four hours, free amoebae will still escape 

 from such treated cysts, but only after several days 

 when transferred to a suitable fresh medium, 



