No. 2.] CENTROSOMES IN THE ANNELID EGG. 8OT 
amphiaster at a corresponding stage. The centrosomes at the 
outer end, however, do not move further apart, but are carried 
into the first polar globule with the nine daughter-chromosomes, 
and there degenerate (Figs. 19-21). 
During the early phases of mitosis the amphiaster presents 
several interesting features. The yellowish brown fibres of the 
central spindle may be seen between the chromosomes after 
they have divided. Between the halves of each chromosome 
is a distinct white band with no such fibres, but a few 
minutely beaded, almost black lines (Fig. 1 7). The spindle 
does not taper to a point at either end, but is truncated, and at 
the truncated ends a ring of extremely minute dots, like the 
centrosomes in color but very much smaller, are brought out in 
many of the clearest preparations (Figs. 14, 15). These dots 
are probably nine in number and appear to be the foci of pen- 
cils of rays extending to the chromosomes. The latter are 
clearly seen in transverse sections of the spindle at a little 
distance from the equator. 
In the very’ late stages of mitosis a delicate Zwischenkorper 
is formed at the junction of the polar globule and egg, but it 
soon vanishes and has nothing to do with the formation of the 
second maturation-spindle. 
The daughter-chromosomes at the inner end of the spindle, 
which at first lie in a circle, later take on an elliptical arrange- 
ment, while the adjacent centrosomes continue to move apart 
and eventually lie one at either end of the ellipse (Figs. 22— 
24). The central spindle, which was formed between the two 
centrosomes at a very early stage, has now reached consider- 
able size, and we have the incipient amphiaster of the second 
maturation-spindle. 
The centrosomes at the poles of this aster are identical with 
the two which lie close together at the inner end of the first 
maturation-spindle (Figs. 14-17), and these are derived by 
division from one of the centrosomes of the primary asters 
(Figs. 8-13). The chromosomes soon are drawn into the 
equator of the spindle, and the latter gradually swings around 
to a position vertical or nearly so, directly under the first polar 
globule (Figs. 25-29). Again, a centrosphere develops around 
