May, 1909.] 
Nuclear Divisions in Convallaria 
499 
the wall (Fig. 6). The chromatin granules are now quite uniform 
in size and shape, and the spireme exists as a single thread 
throughout its entire length (Figs. 6, 6b). 
After synapsis a loosening or unwinding of the thread begins. 
The linin becomes thicker, the granules elongate, and the 
spireme becomes shorter, although it again occupies the whole of 
the nuclear cavity (Fig. 7). Then an apparent division of the 
granules takes place and a double row can be seen (Fig. 8a). 
Occasionally a part of the thread appears still single while the 
rest is double (Fig. 8a). This appearance would be the same if 
the granules were dividing or conjugating. The fact that the 
granules lying opposite each other are so much alike in size and 
shape is all that makes this appear to be a division of the thread. 
There is quite a marked decrease in chromatin matter, however, 
and this, at first sight, would favor a conjugation, but it must be 
remembered that the spireme is rapidly contracting (Figs. 7, 8, 
9). After a short time this doubleness is no longer apparent. 
For the present this will be considered a temporary division of 
chromatin granules. In later studies the author intends to give 
this step more consideration. 
With continued thickening the ribbon begins to show an 
arrangement into definite loops (Figs. 9, 10, 11), which later 
become sixteen chromosomes. Just how these are formed from 
the thirty-two of the spermatogonia has not yet been determined. 
They are of various shapes and sizes, but a common thickness. 
In fact, thickness seems to be the only factor which the sixteen 
chromosomes have in common. They are apparently twice as 
thick as the chromosomes of the sporophyte cell. Since the 
relative stage of development of chromosomes was found to gov¬ 
ern thickness, it was thought advisable to compare for this pur¬ 
pose chromosomes of nearly the same stage. Figs. 17, 21, 26, 
show telophases of cells after the first reduction division, second 
reduction division, and sporophyte cell division, respectively. 
The fact that the daughter chromosomes of F'ig. 17 are so much 
thicker than those of Fig. 26 seems to indicate that the phe¬ 
nomenon after synapsis might have been a pairing of granules. 
There is, usually, one chromosome which is much longer than 
the others. In Fig. 13, it is the fourteenth chromosome. It 
shows a lobing at one end. Many of the chromosomes at this 
stage show a lobing at either, or both ends. (Fig. 12a). This 
lobing is either the beginning of the longitudinal division, or else 
it is a remnant of the double phenomenon noticed shortly after 
synapsis. The nucleolus now fragments and passes into the 
cytoplasm. With the ejection of the micronuclei radiations in 
the cytoplasm appear, and with their polarization the chromo¬ 
somes assume a median position between the two centers of 
radiation. No centrosomes are present. This is the prophase 
of the first reduction division. Fig. 14 is a very late prophase or 
early metaphase. 
