964 Davis. — A Comparison of the Reduction Divisions of 
when present, are not the conspicuous stages of chromatic contraction which 
are so well known to botanists from their apparently universal presence 
in higher plants. For these reasons the writer continues to use the term 
‘ synapsis ’ for that characteristic and relatively long-enduring contraction 
of the chromatic reticula or thread systems that appears previous to the 
differentiation of the spireme of the heterotypic mitosis. 
There is no question in the writer’s mind but that the events of 
synapsis are the result of a true contraction, i. e. a shortening and thickening 
of the strands or threads of the chromatic reticulum. Lawson (’ll) has 
recently expressed the view that in the phase of synapsis ‘ there is no con¬ 
traction whatever of the chromatic substance *, but that the appearance 
of a contraction is the result of an enlargement of the nuclear cavity due to 
a growth which carries the nuclear membrane away from the chromatic 
mass. This view can fortunately be readily tested as to the facts. It will 
be admitted that there is frequently marked nuclear growth throughout the 
period of synapsis which would undoubtedly emphasize a contraction 
of the chromatic material, but can such growth account for the differences, 
in some cases very great, between the size of the nuclear cavity and 
its contained synaptic knot ? It is a simple matter to measure the size 
of the nucleus and of the chromatic mass in optical section through the 
various stages of synapsis. Lawson holds that the chromatic mass remains 
essentially unchanged in its volume and presents evidence for this view in a 
series of figures of Smilacina. These figures, however, are to the writer not 
convincing, inasmuch as the chromatic mass of advanced synapsis (PI. LXXI, 
Figs. 10-17) may be included in a circle having the diameter of the 
presynaptic nucleus (Figs. 1 and 2) with considerable space left unfilled. 
An examination of the figures of any of the species of Oenothera studied by 
the writer will show the outlines of the chromatic mass very much smaller 
and consequently denser during the synaptic stages than in the full-sized 
presynaptic nuclei, and it is his opinion that Lawson’s view will not be 
sustained by the numerous accounts of synapsis on various material. 
The relations among the strands that compose the chromatic reticulum 
previous to and during the synaptic contraction have so far baffled my 
studies. There is apparently in their arrangement no system or order 
of especial significance. In such a complicated and dense mass of elements 
(see figures) it is not difficult to find threads that run closely parallel 
for greater or less distances, but the writer is not willing on the evidence at 
hand to attach significance to these relations. It has not been possible to 
recognize even the elements of a simple spireme and much less conditions 
that might be interpreted as indicating the presence of two parallel spiremes 
of paternal and maternal origin. Fortunately the later history of the 
reduction processes clearly shows that the entire group of sporophytic 
(somatic) chromosomes is formed end to end (telosynapsis) by the seg- 
