20
CHR. P. RAVEN
FIG. 7. The formation of the polar lobe in eggs of Ilyanassa, centrifuged in reverse
orientation before the first polar body had been formed. The second polar lobe arose 70
min later. All eggs, except (a) and (i) show partial return of the cytoplasm towards the
animal pole. The polar bodies were given off before the spindle reached the pole. The lobe
formed at or near its normal field, even when, as in (a), the spindle did not return to the
animal pole, and irrespective of the substances lying in this region at the moment of its
formation. After Morgan, 1933.
always pass through this pole, irrespective of stratification. This occurs
even when cleavage takes place in the centrifuge (Conklin, 1910).
Consequently the place of intersection of the furrows does not necessarily
coincide with the point where the polar bodies have been extruded.
In Ilyanassa eggs centrifuged at early stages, a polar lobe forms at the
CHR. P. RAVEN
FIG. 7. The formation of the polar lobe in eggs of Ilyanassa, centrifuged in reverse
orientation before the first polar body had been formed. The second polar lobe arose 70
min later. All eggs, except (a) and (i) show partial return of the cytoplasm towards the
animal pole. The polar bodies were given off before the spindle reached the pole. The lobe
formed at or near its normal field, even when, as in (a), the spindle did not return to the
animal pole, and irrespective of the substances lying in this region at the moment of its
formation. After Morgan, 1933.
always pass through this pole, irrespective of stratification. This occurs
even when cleavage takes place in the centrifuge (Conklin, 1910).
Consequently the place of intersection of the furrows does not necessarily
coincide with the point where the polar bodies have been extruded.
In Ilyanassa eggs centrifuged at early stages, a polar lobe forms at the