10 MARY JANE HOGUE 



the amoeba a different standard must be used. In one experi- 

 ment already cited the amoebae were treated with neutral red 

 and with janus black no. 2 at 9:30 in the morning. The neutral 

 red color had disappeared at 12:00, noon, but at 4:30 in the 

 afternoon the amoebae were still moving actively. The next 

 day they were dead. 



This is also true of both brilliant cresyl blue and methylene 

 blue. The amoeba moves rapidly after its nucleus and cyto- 

 plasm have both become stained. It is evident, therefore, that 

 these old criteria of the death of a cell cannot be applied to an 

 amoeba which still continues to move. Indeed, one can wonder 

 whether the tissue-culture cells are really dead when their nuclei 

 and cytoplasm have taken these stains. 



When these amoebae are alive they are actively sending out 

 pseudopodia. Usually these come from only one part of the cell 

 at a time, though any part may send them out. The amoebae 

 not only send out pseudopodia, but they move rapidly. As the 

 animals begin to die, progression is less rapid, though the pseudo- 

 podia are formed very quickly. Then gradually the pseudopodia 

 are formed more slowly, then only at one end of the amoeba, and 

 eventually they are simply blebs which flow from one side of the 

 amoeba to the other until finally all motion stops and the amoeba 

 is dead. 



From the fact that locomotion and motion become gradually 

 less and less as the amoeba is dying, it seems evident that the 

 motion of an amoeba and not its reaction to vital stains should 

 be the ultimate criterion of life in the trophozoite stage. 



