284 JOURNAL OF CoMPARATIVE NEUROLOGY. 
corpuscles migrates toward the pole opposite to that at which 
it originates—this migration very probably is correlated with 
disappearance of the nuclear membrane—and after it reaches 
its final position, the centrosome divides into two corpuscles, 
and at the same time the original non-migrating central corpus- 
cles also divides into two, thus forming two central corpuscles 
at each pole. 
The next important event is the formation of the ‘‘aster.”’ 
As figure 9 shows, the somewhat parallel rays formed by mi- 
nute microsomes connect the two poles; that is, the centro- 
somes in both poles are connected with these numerous rays. 
These rays, or ‘‘Halbspindelfasern” of HERMANN, are quite dif- 
ferent from the rest of the aster rays which also arise from the 
centrosomes and radiate outwards in all directions. The ‘‘Halb- 
spindel” rays are stained intensely with reddish color (HER- 
MANN’S method), while the other rays stain very faintly. Not 
only is this so, but the former parallel rays are composed en- 
tirely of coarser granules than compose the latter. Further- 
more, the rays of the latter are directly continuous with the 
cytoreticulum, while the Halbspindelen rays do not show 
such continuation, as far as our observation went. The peculiar 
differences between the ‘‘Halbspindelfasern” and the rest of the 
archoplasm were first reported by Levi (’98), who studied the 
mitosis of the nerve cells of the guinea-pig under pathological 
conditions following mechanical injury, and further Levi sug- 
gested that the ‘‘Halbspindelfasern” are directly derived from 
the acidophile part of the resting nucleolus. Though LEvi has 
pointed out only the ‘‘Halbspindelfasern” as directly derived 
from nucleolus, the writer’s specimens show that a part of the 
central spindle fiber also has been derived in the same way. 
As was mentioned already, the chromosomes in an early 
spireme stage are surrounded by the nucleolar substance, and 
this substance, in the next stage, is transformed into parallel 
rays and extends toward both poles, and finally forms the 
‘‘Halbspindelfasern.”’ This can easily be followed if one com- 
pares the granules which form the spindle with those of the nu- 
cleolar sheath of the chromosomes in an early spireme stage. 
