778 INDIRECT DIVISION OF THE NUCLEI OF CELLS. 
in the process of conjugation as already noticed in Spirogyra 
( fig. 863), is also another method of cell-formation. It occurs 
frequently in Algz, and various groups of Fungi. 
Indirect Division of the Nuclei of Cells (Karyokinesis). —Where 
this occurs, the nucleus, instead of dividing simply and directly, 
assumes various figures before dividing. 
Strasburger described this 
method of division of the 
nucleus in many vegetable 
cells, and a similar method has 
since been shown by several 
observers to occur in animal 
cells. To this process Flem- 
ming has given the name 
karyokinesis, because a spon- 
taneous movement of the nu- 
cleus and its contents is of 
essential importance. 
The first stage in the process 
is the separation of the fibrils 
forming the intranuclear net- 
work, so that they become more 
distinct, and make the nucleus 
appear larger (fig. 1137, a). 
The fibrils then become thicker 
and more separated, thus exags 
gerating the appearance pro- 
duced during the first stage. 
The fibrils next acquire the 
form of long loops, some of 
Fie. 1136. 
Fig. 1136, A, B. Escape of the swarm-spores 
of an @dogonium. c. One in free mo- 
tion. Db. The same after it has become 
fixed, and has formed the attaching 
disc. E. Escape of the whole protoplasm 
of a germ-plant of Wdogonium in the 
form of a swarm-spore. (After Prings- 
which appear to consist of 
two threads (Flemming) ; but 
whether this is their true cha- 
racter, or they are thick fibrils 
which have become hollowed 
out, is uncertain (Klein). In 
the next step the loops cease 
to be single and are very long, each thread forming several, and 
the whole producing a radiating, wreath-like appearance (fig. 
1137, b). The loops then break so that their bends are central, 
the ends pointing outwards and producing a star-like appearance, 
the aster or monaster. The central mass and rays now appear to 
divide into two parts having different planes one above the other 
(fig. 1137, c, d), except at the periphery of the loops, where for 
a time the two stars remain connected, though soon they sepa- 
rate, producing the double star, or dyaster, which in many cases 
is the only form of star that is seen, the monaster apparently 
not occurring at all. The two stars of the dyaster then recede 
from each other so that their centres occupy opposite poles of 
heim. ) 
ae, ee ee eT Toe 
