CENOTHERA MUT. LATA AND (K. MUT. SEMI LATA. 569 
single mother-cell. a. There are 6 daughter-chromosomes moving 
towards either pole, and at the equator two fragments which together 
are equivalent to a single daughter-chromosome, h. Eight daughter- 
chromosomes are moving towards either pole of the spindle, and in the 
centre are two small fragments. Apparently these four fragments are 
formed l^y the two halves of the extra chromosome which split at the 
heterotypic metaphase. 
Fig. 28. — Anaphase of homotypic division, showing 8 daughter- 
chromosomes going to either pole of one spindle. 
PLATE 3d. 
Fig. 29. — Late anaphase of the homotypic division, showing the 4 
chromosome groups of the tetiad. The upper pair contains 7 
chromosomes and the lower pair 8 chromosomes, in each group. 
Fig 30 a and h . — Homotypic mitosis in two sections. In h 6 
chromosomes are seen at one ’pole of the spindle, the remaining 2 
Ijeing in section a ; 8 are approaching the other pole of this spindle. 
In the second spindle there are 6 daughter-chromosomes at one pole 
and 4 at the other. The 4 remaining daughter-chromosomes on this 
spindle are degenerating in the equatorial region. 
Fig. 31 a and h . — Late homotypic anaphase, a. On the lower spindle 
each anaphase group contains 8 chromosomes. On the other spindle 
each group has 7 chromosomes, section h showing 5 chromosomes close 
together and two displaced, one of the latter (c) having also been cut 
by the knife so that the greater part of (c) appears in section a. 
Fig. 32. — Degenerating anther. Mother-cells connected by broad 
bands of cytoplasm. Cytoplasm scanty. No tapetal cells differentiated. 
Fig. 33. — Mother-cells degenerating. Nuclei as dark chromatic 
masses passing through the walls. Tapetum not differentiated. 
Fig. 34. — Another type of degeneration, tapetum not differentiated. 
The mother-cells are in contact, the chromosomes short and scattered, 
and passing through the walls. 
Fig 35. — A mother-cell in another condition of degeneration. The 
cytoplasm a coarse, dark, highly vacuolate reticulum. The nucleus 
has disappeared or is represented by the dark mass at the centre of the 
cell. 
GE. biennis lata. 
Fig. 36. — Normal polar view of heterotypic metaphase, showing 15 
chromosomes. 
Fig. 37 a and h . — Profile view of heterotypic spindle in two sections 
