Relation between Nucleolus and Chromosomes. 
al 
7 
also, as Child holds in the case of Arenicola marina, several fibers may 
have united into one. Some of the astral rays interdigitate above the equa- 
torial plate. All seem to merge into the cytoreticulum. Frequent cross- 
connections are seen. The central ends of the rays are seen to penetrate 
for some distance into the centrosphere, but they could never be traced 
as far as the central granules (centrosome). It is very probable that 
the rays are centrally continuous with the reticulum (very delicate, and 
sometimes alveolar in structure) of the centrosphere. The spindle now 
begins to rotate and ultimately assumes a radial position. This rotation is 
effected very rapidly. In 10 to 15 minutes more the first polar body is fully 
formed. Thus it requires about 1 hour for the first polar body to form, 
which agrees with what was observed in the case of living eggs. To 
recapitulate, the single aster appears about 10 minutes after transference 
of the eggs to sea-water. At twenty minutes there are two asters some 
distance apart, with rays extending through the ruptured nuclear wall and 
becoming attached to the growing chromosomes. At 45 minutes the first 
polar spindle is fully formed and in process of rotation. The last 20 or 
30 minutes represent the prophase of maturation. The spindle moves rap- 
idly into a radial position, metaphase and anaphase are passed through very 
quickly, and after 60 minutes the first polar body is fully formed. 
In the radial position, the spindle is at first comparatively slender and 
sharply pointed at the ends (figs. 66,67). The central sphere often contains 
two centrosomes (fig. 66). The spindle moves bodily toward the periphery 
and as it approaches the cell-wall it becomes stouter, somewhat barrel-shaped, 
slightly shorter, and its ends less pointed (fig. 69). This change of shape 
and size is undoubtedly due to the resistance met with by the spindle in 
its passage through the cytoplasm. The outwardly pointing rays of the 
distal pole disappear, the horizontal rays are at first bent inward, and all 
eventually disappear into the cytoreticulum as the outer pole of the spindle 
is forced out of the egg to form the first polar body (fig. 70). The rays 
of the central aster have also meanwhile become shorter and less definite, 
while the centrosphere has become more reticular, somewhat flattened, very 
much less definite, and in the later stages of the first polar spindle is scarcely 
to be recognized. In the late anaphase the spindle exhibits a distinct mid- 
body (Zwischenkorper) in the form of swellings or small granules in the 
equatorial plane of the spindle. This marks the line of division between 
the first polar body and the central pole of the spindle. Traces of spindle 
fibers are at first visible in the first polar body, but these gradually disappear, 
and the chromosomes (about 18 double dumb-bell-shaped bodies, often 
assuming the form of “tetrads’’) are seen to lie in a homogeneous or finely 
granular light-staining substance (figs. 70, 71). In my study of the living 
eggs I found a single instance of a division of the first polar body. Study of 
sectioned material failed to contribute a duplicate of this solitary example. 
