Nov., 1912.] The Reduction Division in Fuchsia. 
5 
middle. The next division is longitudinal and the resulting nuclei 
form the tetrads. The nucleoli fragment and pass into the 
cytoplasm during both the first and second divisions. 
In Agave viriginica (22) Schaffner described bivalent proto¬ 
chromosomes which formed a long delicate continuous spirem 
with a single row of chromatin granules. Synizesis follows 
during which there is no union of the spirems. A study of living 
material did not show any noticeable contraction of the nuclear 
contents and the nucleoli were usually found occupying a central 
position in the nucleus. While the chromatin granules undergo 
transverse division, the spirem shortens and thickens and then 
twists up into twelve loops of different size and shape which are 
pressed against the nuclear wall. These loops then break apart 
into four large, three ring shaped and five small irregular chro¬ 
mosomes. One or two nucleoli are present which may be thrown 
out into the cytoplasm. The spindle is bipolar and at the first 
division the chromosomes divide transversely but the second 
division is longitudinal. 
Miss Hyde in her paper on Hyacinthus (11) did not find 
definite protochromosomes nor a splitting of the spirem. She 
observed a continuous spirem which formed eight definite loops. 
These loops break apart and form eight chromosomes of different 
characteristic sizes and shapes. 
There has been much controversy as to the real nature of the 
contraction generally observed in the early stages of the division 
of reduction cells. In most cases this contraction is accompanied 
by an enlargement of the nucleus due to the expansion of the 
nuclear wall. McClung (15) has suggested the term synizesis, 
to be used to mean the contraction as distinct from synapsis, 
synapsis being restricted to the fusion of simple chromosomes into 
multiple ones. Lawson (12) has recently investigated the problem 
and his interpretation of synizesis is simply that it represents a 
growth period of the nucleus—a period during which there is a 
great increase in the amount of nuclear sap, which results in a 
distention and withdrawal of the nuclear membrane from the 
chromatin. As to why the nucleus should swell so much immedi¬ 
ately before the reduction division he answers as follows. Each 
cell is charged with sufficient food substance for the production 
of the tetrad. Moreover there are two divisions which follow 
one another in quick succession. The pressure of the cell sap acting 
from within causes the nuclear membrane to distend and the 
nuclear cavity to expand. The expansion is at first gradual and 
continuous until the nuclear cavity grows to twice or even three 
times its original size. 
As the growth proceeds the membrane is gradually withdrawn 
from the chromatin mass within. The result of this withdrawal 
of the nuclear membrane is the formation of a large clear area of 
