1887] The Significance of Sex. 159 
may divide, and so split the spindle (Fig. 124), and often the two 
stars first arise close together, and move later to opposite poles. 
We must also notice Rabl’s discovery of a spindle intact in the 
nucleus, which rotates into its position (see Fig. 113, c) through 
an angle of 
In what condition is the chromatin in the resting nucleus? It 
may be present as a fine or as a coarse reticulum, closely inter- 
penetrating the parachromatic reticulum, and perhaps fused with 
it. In the germinal vesicle it is present as a nucleus, which be- 
comes transformed into the reticulum before division. The next 
change this reticulum suffers is its transformation into a mitom,— 
z.é., a filament,—which, while it is very long and closely balled up, 
may not be distinguished from a reticulum. Some nuclei rest in 
this phase, or in subsequent phases of its shortening and conse- 
quent thickening. When thick it has been found to be com- 
posed of granules that fuse to form microsomata, so that finally 
the mitom is one microsoma thick. The next phase is one in 
which the mitom segments into loops or filamentous karyosomata. 
Some cells rest in this phase. (See Fig. 124.) When the segmen- 
tation occurs early, while the reticulum is being transformed into 
the mitom, we get a condition of things represented in Figs. 113 
and 45. The karyosomata are apt to be short or corpuscular in 
generative cells. (See Figs. 122 and 123.) 
Now we have two ways in which the karyosomata are sepa- 
rated into two groups to form the daughter-nuclei. In one they 
are separated without accompanying division, as in Fig. 124. In 
the other they divide in such a way that each half of the karyo- 
soma is destined to pass into different daughter-nuclei. In this 
case we get two forms. In one form the karyosomata, if they 
are short, become arranged into a nuclear plate in the equator of 
the spindle, and by division and separation of the halves we get 
two daughter-plates that pass to the poles, and become the 
daughter-nuclei, but if they are long, they lie along each spindle- 
fibre and are bisected in the equator as in Figs. 101 and 115. In 
the other case the daughter-segments are produced by a longi- 
tudinal splitting of the loop, as shown in Figs. 114, 118, and 119, in 
which splitting usually occurs early, while the spirem figure still 
persists, and in this case no true equatorial plate may form, but 
be only the expression of separating loops passing each other on 
the way to their respective ogg Between all these different 
VOL. 
XXI.—NO, 2, 
