552 
Lewis . — The Behaviour of the Chromosomes 
Summary. 
1. The chromatin of the resting nucleus exists in the form of rather 
large granular lumps connected by delicate anastomosing strands of linin. 
The number of such lumps is always greatly in excess of the number of 
somatic chromosomes typical of the species. There is therefore no evidence 
to be found here in favour of the idea of prochromosomes. 
2. The nuclear content approaches the synaptic condition while still 
in the form of a reticulum. No spirem is formed previous to synapsis. 
3. The term synapsis should be used to denote the definite stage 
of contraction which is observed to occur always in spore-mother-cells and 
which is universally recognized as a normal phase in the process of 
meiosis. 
4. Synapsis does not affect the conjugation in pairs of the somatic 
chromosomes of the maternal and paternal ancestry respectively arranged 
side by side. 
5. As the chromatin thread recovers from synapsis, it is frequently 
seen to reveal a double nature and this is interpreted as due to longitudinal 
fission. Since this double nature is never prominent and eventually almost 
entirely disappears, it is not considered of paramount importance in the 
final development of the chromosomes. 
6. The spirem becomes somewhat regular and forms loops in some 
cases, although the number of loops is not always the same as the number 
of bivalent chromosomes. Some of the pieces become approximated after 
cross-segmentatipn. The spirem often presents an extremely ragged reti- 
culate structure just before cross-segmentation. 
7. The bivalent chromosomes separate during metakanesis, one member 
passes entire to each daughter nucleus and thus affects a qualitative division. 
The retreating chromosomes are seen to split longitudinally as they approach 
the poles. It may be questioned whether this split bears a relation to the 
split of the early prophase, since that fission had seemed to entirely dis- 
appear. 
8. The chromosomes of the first mitosis completely lose their identity 
in the daughter nuclei, which pass into a complete resting stage and thus 
all speculations as to their continuity in the following homotypic division 
is purely theoretical, having no basis whatever in fact. 
9. The spirem of the second division is formed singly and never under- 
goes longitudinal fission as suggested by Miss Ferguson for the genus 
Finns . The chromosomes formed from this spirem are rods, either straight, 
hooked at the ends, or bent in the middle. 
10. The chromomere and not the chromosome is regarded as the 
idioplasmic unit which, due to its action on the unstable cytoplasm, is 
responsible for the appearance of characters. 
