166 TRANSACTIONS OF THE [may 11, 
asters diverge but little while their growth continues, then the 
state of things shown in Fig. 3 will follow. 
The nuclear membrane now gradually fades away, first disap- 
pearing in the neighborhood of the asters, and the tetrad chro- 
mosomes are drawn up into the spindle. A vast amount of the 
chromatin is left as a very coarse stranded reticulum or skein 
lying in the cytoplasm, where it degenerates and finally fades 
away, though it sometimes persists until the first polar spindle 
is in place. (Fig. 4.) The nucleolus can be traced through all 
stages previous to the one just described. The latest period at 
which I have observed it was in a stage slightly later than the 
one figured. It then appears in the mass of discarded chroma- 
tin as a dark staining body, variable in shape and size though 
always considerably smaller than in previous stages. 
With the arrangement of the chromosomes in an equatorial 
plate, the first polar spindle is completed. It lies tangentially 
on the periphery of the mass of discarded chromatin. The 
spindle now rotates through 90° and assumes a radial position. 
(Fig. 5.) At this stage the length of the spindle is nearly one- 
third the diameter of the egg. At each pole is a well defined 
light staining centrosphere, containing a double centrosome. 
The centrosphere is perfectly homogeneous and shows no trace 
of any darker area surrounding the centrosomes. <A noticeable 
feature is presented by the rays. These are relatively of great 
length, many exceeding that of the entire spindle. Those that 
pierce the equatorial plane, external to the spindle, show a 
marked curvature toward the axis of the latter. This curvature 
is greater in those lying nearer the spindle. At this period the 
egg shows a marked polarity, which was not so obvious in 
earlier stages. This is brought about by the collection of the 
deutoplasm at the lower pole, leaving the region at the upper 
pole surrounding the spindle relatively free from yolk granules. 
A slight flattening or depression of the surface of the egg next 
the external aster is also to be seen the stage just described. 
(Fig. 5.) During the halving of the tetrad groups no change 
takes place in the achromatic figure until mid or late anaphase, 
when the two inner centrosomes diverge considerably in a di- 
rection perpendicular to the axis of the spindle, the centrosphere 
meanwhile elongating in the same direction. 
The telephase, therefore, shows the two centrosomes wide 
apart, one at each pole of the now somewhat fusiform centro- 
sphere, and the rays show a tendency to group themselves about. 
these poles as foci. The dyads left in the egg, after the expul- 
sion of the first polar body, lie at the outer side on the peri- 
phery of this incipient spindle, stretching in a curved row from 
