The individuality of the chromosomes and their serial arrangement, etc. 135 
of Organization in the chromosomes of the somatic nuclei in many species, 
and that as Overton (1909) shows this may extend to a pairing of two 
complete spirems. 
In Carex aquatilis there is, as has becn shown above, a permanent 
serial arrangement of the chromosomes, especiaUy during the history of 
the somatic nuclei. In synapsis, however, the series of individual chromo- 
somes is changed to a slender continuous chromatic spirem. After the 
contraction and pachyneme stage there emerge the bivalent chromo- 
somes of diakinesis. The composition of these pairs as influenced by the 
events of synapsis has already been discussed. 
In the thick spirem and the stagcs following it, I find no evidence 
of a strepsineme stage. The rounded chromosomes appear in pairs. They 
are nearly isodiametrical, as in the case of various insects, with no apparent 
twisting or Crossing of parts. Hence in Carex aquatilis there is no possi- 
bility of such phenomena as Janssens (1909) describes under his “chiasma- 
typie” theory. If, however, the loops of the bivalent spirem should not 
straighten out as the spirem enters the heterotypic equatorial plate but 
should cross each other, there would be opportunity at this stage for 
chiasmatypic readjustment of parts of the paired spirems similar to that 
which Janssens describes between parts of paired chromosomes. 
The double spirem appearing in diakinesis passes into the equatorial 
plate where two complete series part. It is, however, possible that in 
the more or less twisted condition of the double spirem just previous to 
the formation of the equatorial plate of the heterotypic division, there 
may be a rotating of certain pairs in the double spirem so that a con- 
stant association of the same chromosomes may not prevail. The marked 
persistance of the serial relationship, however, suggests strongly that 
each of the two series may remain as such throughout all stages of nuclear 
development. Even though there be a rotation of varions pairs there 
are certain parts of the series in which the chromosomes remain in the 
same alignment. This decreases the opportunity for a simple chance 
distribution of the chromosomes in the reduction division. 
From these observations it would appear that the serial arrange- 
ment of the chromosomes is an important factor influencing the degree 
of Chance distribution of the maternal and the paternal chromosomes. 
The studies here reported were pursued at the University of Wisconsin 
during the years 1909 — 11, and at the New York Botanical Garden 
during 1911 — 1912, and throughout the investigation the writer has 
had the helpful criticism and direction of Professor K. A. Harper. 
