AMOEBAE VERSUS TISSUE CELLS 9 



After the granules have entered the endoplasm, they circulate 

 freely through it. Sometimes two or more will unite and occa- 

 sionally a vacuole will form about these fused granules. Some- 

 times there will be as many as three or four clumps of granules 

 in one vacuole. These vacuoles are heavy and lag behind in the 

 posterior part of the amoeba. Eventually they come in contact 

 with the outer edge of the amoeba. After that they soon break, 

 discharging the pigment granules to the outside. Some of the 

 granules remain attached to the amoeba, others, more forcibly 

 ejected, float away in the medium. In this way the amoeba 

 gets rid of the melanin pigment. After twenty-four hours most 

 of the amoebae had given off the granules and were moving about 

 freely among the granules without taking them in again, at least 

 not in such large quantities as when the granules were first intro- 

 duced into the hanging drop. The amoebae never digested the 

 melanin pigment. 



Small mononuclear blood cells were present in large numbers 

 in the tissue cultures of spleen. These the amoebae took in, 

 carried them about for a while, and then gave them off. Several 

 of them would often remain sticking to the posterior end of the 

 amoeba along with many pigment granules. All this weight did 

 not seem to retard the movement of the amoeba. 



These results are somewhat similar to those obtained by Smith 

 ('21) with tissue-culture cells, except that the tissue cells take 

 in the melanin pigment at all parts and the pigment granule 

 must always be horizontal to the surface of the cell where it is 

 entering. He notes the formation of vacuoles, but could not 

 determine the ultimate fate of the granules, as the life of the 

 tissue-culture cells is short, and they died without discharging 

 or digesting the granules. 



DEATH 



Ordinarily when the nucleus and cytoplasm of a tissue-culture 

 cell have taken methylene-blue or brilUant cresyl-blue or neutral- 

 red stain, the cell is said to be dead. Again in tissue-culture 

 cells, when the color of the neutral-red granules fades and they 

 become clear, the cell is thought to be dead (Lewis, '19). With 



