No. 2.] CENTROSOMES IN THE ANNELID EGG. 197 
toward the surface, and appear as two distinct dots in the 
midst of a clear yellow centrosphere at either end of the spindle. 
The fibres of the central spindle differ in color from the 
other fibres of the asters, staining yellowish brown with orange 
G (or red with Bordeaux) much like the centrospheres, while 
the other rays are purplish. The chromosomes, moreover, do 
not, at first, lie directly between the two poles, but upon the 
surface of the central spindle (Fig. 10); later they seem to 
insinuate themselves between its fibres (Fig. 11). 
The remains of the germinal vesicle are evident for some 
time after the spindle has assumed its definitive position, but 
gradually fade away (Figs. 12-15). Having reached the meta- 
phase the spindle remains without apparent change until the 
egg is fertilized. The astral rays extend for a long distance 
into the cytoplasm, intercross with one another, and break up 
at the ends into the cytoreticulum, which is now much more 
delicate and finer than during the earlier stages when the 
paranucleus was disappearing. 
It is difficult to understand why the process of karyokinesis 
should be suspended at this time, for the apparatus of division 
is apparently ready, the asters are well developed, the chromo- 
somes in position at the equator of the spindle, and the centro- 
somes have divided in anticipation of the next mitosis (Figs. 
13-16). 
(d) Observations upon the Unfertilized Living Eggs. 
During the past summer I have examined a large number of 
living eggs to confirm the results obtained from the study 
of preserved material. Full-grown eggs taken from the body- 
cavity of the female and examined under slight pressure in- 
variably show a germinal vesicle with even contour, and inside 
the vesicle the nucleolus. The cytoplasm is, at first, uniformly 
opaque, but in two or three minutes a number of light points 
appear, and soon the whole cytoplasm is studded with a multi- 
tude of secondary asters. Since the yolk is repelled from the 
centre of the asters, the latter appear as transparent spots in 
an opaque field. After about four minutes two of the asters 
(primary asters) become especially distinct and the others 
