Oll the Effect of Centrifugal Force on the Frog’s Egg. 
389 
normal development of certain centrifuged eggs has been used as an ar- 
gument for the position tliat the deutoplasm moved by the centrifuge 
has little or no effect on polarity. If this be true the polarity is determi- 
Fig. 5. 
Section through the equator of a mitotic fignre 
in an egg of Baita pipiens that was centrifuged 
in the two cell stage, centrifugal force = 
2771 X gravity for one minute. The yolk 
platelets and pigmcnt granules, in heing preci- 
pitated, were stopped by the spindle and piled 
up on it. 
Fig. 6. 
Group of chromosomal vesicles surrounded by 
four asters in a horizontal section of the egg 
of Chorophilus triseriatns that was placed in 
the centrifuge in the four cell stage, centri- 
fugal force = 565 X gravity for 45 minutes. 
ned by the protoplasm. If the polarity be determined by the cytoplasm 
alone, currents might destroy the relation of the polar axes of various 
Fig. 7. 
From a section of the same egg shown in fig. ß, showing a nuclens, one of whose asters has apparently 
divided and one of the products of the division has moved away. 
regions to one another, just as would be the case if a magnet were melted 
and its substance stirred. 
Another cause for the abnormal development of centrifuged frog’s 
eggs might be abnormalities in the mitotic figures. I have previously 
