CYTOLOGICAL STUDIES OF CENTRIFUGED EGGS 627 
stages the animal halves of the blastomeres separate widely and a 
clear fluid appears along the line of division. How far these effects 
are artificial I cannot state since comparative studies with differ- 
ing reagents have not been m_ade. Unfortunately most of the 
Harpswell eggs were killed in picro-acetic, which while giving 
good figures of the asters and spindles does not appear to preserve 
the cytoplasm particularly well, forming a coarse reticulum. 
Eggs preserved in corosive acetic are much more finely granular 
and appear in other respects better preserved. 
In many eggs the first division is at right angles or oblique to the 
plane of stratification, cutting off a cell free from yolk and another 
containing all the yolk. These eggs are those in which the centri- 
fuged axis did not coincide with the polar axis. They were not 
isolated unfortunately to see whether the presence of the yolk 
ball would cause abnormalities in development, but it seems 
probable that this would be the case; for, the compact yolk 
seems to interfere seriously with the segmentation. 
Unless the eggs are in excellent condition normal embryos do 
not develop. Itisalsonecessary to keep the eggs under favorable 
conditions, free from slime and sperm, to obtain the character- 
istic larvae, the pilidia. My studies were confined largely to the 
inmiediate effects of the centrifuging on the eggs and insufficient 
care was given to the embryos. In some lots of centrifuged eggs 
I have, however, obtained as high a percentage of pilidia as in 
control sets, but the observations do not suffice to show more 
than that some eggs develop normally. There can be little doubt 
that the yolk ball introduces abnormalities, but how far I cannot 
state. 
Influence of centrifuging on the karyokinetic figure 
The eggs of ('erebratulus are particularly well suited to study 
the influence of centrifuging in the various phases of karyokinesis 
and the evidence throws some light, I believe, on the nature of the 
asters and spindles. 
If centrifuged at once and allowed to stand the polar spindle 
forms near the inner wall of the nucleus. As the spindle develops 
the chromosomes are drawn or move to its equator. The rest 
