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LIFE S BEGINNING ON THE EARTH 



tion). We may observe an oil-drop of any description: 

 olive oil, cotton-seed oil, rape-seed oil, oil of clove, or any 

 other plant oil. The oil-drop is placed in water, to which 



Fig. 63 a. Moving Oil-Drops Showing Amoeba-like Movement 



This picture and the next were obtained through the courtesy of A. L. 

 Herrera of Mexico City. The oil is a mixture of one part of olive oil with 

 four parts of gasoline; it floats in a water solution containing 6 per cent 

 soda. The photograph shows the distortion of the droplets by protrusions, 

 giving some of them an ovoid or dumb-bell shape. 



should be added some other substance which tends to inter- 

 act with the oil-drop or to dissolve it. 



Figure 63 shows the movements of oil-drops of this kind. 

 The photograph on top is a "flash" from which we recog- 

 nize the elongated and distorted shape of the moving drops. 



