CYTOLOGICAL STUDIES OF CENTRIFUGED EGGS 623 
of force conception, still puts that assumption on rather a question- 
able basis. 
Lillie has recently pointed out that he has found a decisive 
proof of the center of force hypothesis in the behavior of the spindle 
when the basic granules of the egg are driven into its field of action. 
These granules now become arranged in chains that represent 
the polar rays and replace the original material of these rays. If 
Lillie's proof is cogent, it is the most important fact yet discovered, 
by means of the centrifuge, in relation to the process of karyo- 
kinesis. Therefore I propose to examine it as criticallyaspossible, 
since it involves our entire conception of the meaning of the 
karyokinetic figure. The egg of Cerebratulus furnishes the same 
kind of evidence as that adduced by Lillie, so that I am able to 
consider his conclusion from the evidence of my own observations. 
It is true, as Lillie has found, that when the rays from the poles 
of the spindle pass into a region rich in basic granules these gran- 
ules appear to be arranged bead-like. From this fact Lillie argues 
that the beads have taken the place of the fibres under the influ- 
ence of the outpouring of the centrosomes or centers of some sort. 
But it should be remembered that in all normal cells containing 
such granules these become arranged along the lines of the spindle 
fibres as the fibres pass by them. Possibly when the alveoli are 
narrow the granules may become imbedded in the fibres. This 
point is too difficult to determine with certainty. The granules 
appear to lie in the walls of the larger alveoli and it is through these 
walls that the astral fibres pass. It is not surprising, therefore, to 
find the granules arranged along the fibres to which they appear 
to be stuck. 
If these granules are sufficiently numerous they may obscure 
the less stainable fibres, and hence lead one to conclude that the 
granules have replaced the fibres. It seems to me that Lillie may 
have fallen into this error but whether he has or has not, the evi- 
dence that he adduces is of such a kind that I venture to question 
the certainty of the interpretation. I do not wish to speak dog- 
matically on the point, for I realize how difficult it is to be sure 
that fibres cause the orientation of the granules and that the 
granules take no part or play only a secondary role in the process. 
