274 7- P- McClendon 



In the above experiment there were in 20 days, 30 divisions in the 

 three series from the centrifuge and only 10 in the control. Dur- 

 ing the five days in which the control lived, there were 16 divisions 

 in the centrifuged series. 



Many experiments with Paramoecia centrifuged from one hour 

 to six days, both with and without gum, gave similar results, only 

 the effect was not so marked in the longer periods. All the above 

 lots were from the same culture. 



It was stated above that many Paramoecia are misshapen in 

 the centrifuge. The end into which the nuclei are precipitated is 

 bulged out by them, and in a few cases the other end is also bulged 

 out (by the accumulation of substances of low specific gravity .^) 

 giving the animal the form of a dumb-bell. I fed Paramoecia on 

 egg yolk, and globules of a dark brown fatty substance were formed 

 in the endoplasm in such numbers as to make it appear black. 

 These black Paramoecia were subjected to as great a centrifugal 

 force as they could stand, in some cases for two or three days. 

 The fatty substance being of low specific gravity, accumulated 

 in the end opposite the one into which the nuclei were precipitated. 

 The result was a pear shaped body, the large end being black and 

 the small end of the normal Paramcecium color. So great was 

 the difference in the specific gravity of the two ends that the animal 

 could only with difficulty assume a horizontal position or turn the 

 small end uppermost. No marked increase in rate of growth or 

 reproduction that could be ascribed to the stimulating effect of 

 the lecithin in the yolk was observed. 



It was noted above that some of the Paramoecia when taken 

 from the centrifuge appeared to be undergoing division. More 

 often the body was abnormally elongated, with or without a con- 

 striction in the middle. In these cases the end not containing the 

 nuclei shriveled after a day or so, and the animal died within a 

 week. It may be that the centrifugal force keeping the nucleus 

 in one end prevents its division though the animal is large enough 

 to form two, and the portion around the nucleus attempts to form 

 itself into an individual, thus causing the constriction in the middle. 

 If such a division is actually completed I have never observed it. 



When Paramoecia are centrifuged without gum in the medium, 



