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1909] GRIGGS—MITOSIS IN SYNCHYTRIUM 345: 
center of the chromatic mass (figs. 24, 25), but very soon it is evident 
that the focus is beyond the condensed chromosomes (fig. 24). AS 
the rays increase in strength the focus is shifted, until there is a 
considerable interval between the center and the chromatin (jig. 27). 
In this stage, since the chromatin is condensed to its minimum 
volume, the aster is so very much more prominent than the chromatin 
that the latter is likely to be overlooked altogether, making it appear 
that the cyst has no nuclei, but only asters! The chromatic mass 
soon enlarges, however, and rounds off into the spherical karyosome 
of the resting nucleus (figs. 27, 28). Up to this stage the chromatin 
lies suspended in the cytoreticulum, without any apparent relation to it. 
The appearance of the karyosome, however, marks the resumption 
of definite relations of nucleus and cytoplasm in the formation of a 
vacuole around the chromatin (fig. 28). This vacuole is at first 
bounded only by the meshes of the cytoplasm, but soon the rays of 
the aster bend around it and form the heavy nuclear membrane which 
incloses it (figs. 29, 30), as previously described by KusANno (10) and 
myself (4). When the nuclear membrane is complete, the aster 
gradually disappears; the rays first become much more numerous and 
finer; the center gradually becomes diffuse and stains less deeply 
(fig. 4); and finally the aster is transformed into a condensation of 
_ cytoplasm as previously described (figs. 31, 20, 3): 
During the disappearance of the aster, however, the nucleus usually 
enters into the prophases of the next division, so that only seldom is 
4 cyst found where the nuclei are still in their vegetative condition 
when the asters are in their last stages. On the other hand, it is not 
at all unusual to find that the new spindle has already formed, before 
the aster has disappeared, and in rare cases the anaphase of the suc- 
ceeding division (fig. 20) may be reached before the old aster is com- 
pletely gone. The disappearance of the aster probably occupies a 
Period of somewhat definite length, while the rapidity with which 
the mitoses succeed each other varies greatly in diferent cysts. 1 
Was this lack of correspondence between the cycles of astral and 
nuclear metamorphoses that made it necessary in the former paper 
on this subject to state some conclusions provisionally that may now 
be positively established. 3 
From their function of forming the nuclear membrane, the asters 
