52 Overton. — On the Organization of the Nuclei in the 
has observed that it may or may not be present in Liliutn speciosum , and 
believes that it has no special significance. It appears that the phenomena 
of second contraction may occur in plants like Lilium and Podophyllum , 
which possess comparatively long chromosomes. It certainly does not 
occur in the plants with short chromosomes which I have considered, and 
I do not believe that any importance can be placed upon this phase. 
Resume. 
i . In the somatic nuclei of Thalictrum purpurascens and Calycanthus 
jloridus , the chromosomes are represented during rest by definite visible 
bodies, the prochromosomes, which are arranged in parallel pairs, with 
apparent linin intervals. These heterogeneous spirems, the homologous 
portions of which have become early associated in pairs, probably remain 
distinct throughout the life-history of the sporophyte. 
2 . Prochromosomes are also present in the resting nuclei of the germ 
cells of these plants and Richardia africana in exactly the same arrange- 
ment and form as in the somatic nuclei. The homologous parental elements 
are, therefore, already associated in pairs when they enter the reconstruction 
stages of the germ nuclei. 
3. During the prophases of the heterotypic division these parallel 
parental heterogeneous spirems become more distinct, and the general linin 
framework of the nuclei disappears. 
4. The synaptic contraction, or massing of the nuclear elements, which 
is regarded as a natural phenomenon, is a gradual process, during which 
the homologous parental spirems may become more closely associated. 
During synapsis the parental spirems remain distinct. 
5. Since the homologous portions are most closely associated during 
post-synaptic stages, conjugation, interchange, or mutual influence probably 
occurs during the spirem stages. 
6. Association of homologous chromosomes probably occurs during 
fertilization or shortly thereafter, but the actual interchange of parental 
parts or influence occurs during synapsis or related stages (see 5). 
7. There is no continuous chromatin spirem at any stage. 
8. There is no second contraction figure, which is regarded as having 
no significance in the reduction process. 
9. The chromosomes persist as definitely limited visible bodies through- 
out all the prophases of the heterotypic division. 
10. Each of the two parts composing each diakinetic chromosome 
represents a somatic chromosome. Homologous somatic chromosomes have 
become associated in parallel pairs very early in development of the 
sporophyte. No folding process to form these bivalent chromosomes seems 
possible. 
