218 Sargant. — Formation of the Sexual Nuclei 
Second longitudinal fission of the chromosomes. The 
segments of homotype chromosomes appear homogeneous 
throughout the karyokinesis (D-F). Heterotype segments 
are differentiated shortly after their formation. Each consists 
of a length of erythrophilous ribbon bearing a row of cya- 
nophilous dots on either margin (I). This differentiation 
disappears with the nucleolus and nuclear membrane. The 
segments then look homogeneous (K). Whether any trace 
of the second fission remains in their structure is uncertain. 
Contorted shape of the chromosomes in the nuclear plate. 
The segments of the homotype chromosome are nearly 
parallel to each other, and they separate from each other 
with great regularity, usually from one end (E). This is 
not the case with the heterotype chromosome. The seg- 
ments are tightly twisted on each other, they may separate 
from near the middle of the chromosome or (more rarely) 
from one end. The result is that the separating chromosomes 
are much contorted, and adjacent ones may be of a very 
different shape (K). 
Shape of diaster -segmen ts. As a necessary consequence 
of their method of separation, segments of homotype diaster 
are generally hooked (F), the heterotype diaster-segments 
V-shaped (M). No great importance is to be attached to 
this distinction. 
Appendix on Methods. 
A. FIXING. 
Anthers fixed in absolute alcohol were usually uncut. Those fixed 
in any of the three solutions given below were either halved trans- 
versely or cut at both ends to ensure penetration. 
Hermanns solution ( alcoholic ). 
10 % aqueous solution of platinic chloride 3 c.c. 
1 % osmic acid (aqueous) . . .8 c.c. 
Glacial acetic acid . . . 2 c.c. 
Absolute alcohol . . . . .27 c.c. 
