~ 
CELL SIZE AND NUCLEAR SIZE 2) 
first formed this spindle hes near the middle of the egg, and if the 
division wall were to form while the spindle lies in this position 
a polar body would be formed whose diameter would be to that 
of the egg as 1:1, 1 : 2, or at the least 1:3. Later the spindle 
moves toward the periphery until one pole comes into contact 
with the cell membrane. The membrane then protrudes over 
this pole and into this protrusion the end of the spindle moves; 
at the same time the spindle itself constantly grows shorter, 
until finally the spindle is but little more than double the diameter 
of the polar body, and in the separation of the polar body the 
division wall passes through the equator of the spindle. In 
Crepidula plana the first maturation spindle shortens to about 
half its original length; during the metaphase its maximum length 
is about 42u, at the time when the polar body is being separated 
it is only 24u long. 
By means of centrifugal force it is possible to prevent the 
spindle from moving from its first position and also from short- 
ening, and under these circumstances giant polar bodies are 
formed, sometimes quite as large as the remainder of the egg. 
In all such cases the division wall passes through the equator 
of the spindle. Evidently the factors which bring about this 
most unequal of all cell divisions are (1) the eccentricity and (2) 
the shortening of the maturation spindle. 
The second polar body is but slightly smaller than the first, 
nevertheless the spindle is much smaller, its maximum length in 
Crepidula plana being 18u; correspondingly it shortens much less 
in the anaphase than the first polar spindle, being almost as long 
when the division wall begins to form as in the metaphase. 
Though the second polar spindle may appear at some distance 
from the point at which the first polar body was formed, and 
although its axis may lie at right angles to that of the first polar 
spindle, it invariably rotates into the axis of the latter and the 
whole spindle moves toward the surface until its outer pole 
comes to lie immediately under the first polar body, and here 
the second polar body is pushed out. In this case the principal 
factor which causes the inequality of division is the eccentricity 
of the spindle. If the spindle is prevented by pressure or cen- 
