2 
The Ohio Naturalist. 
[Vol. XIII, No. 1, 
united in pairs. He did not find a conjugation of two threads 
during synapsis. He mentions a slight resting stage between the 
first or heterotypic division and the second, homotypic division, 
but does not speak of any longitudinal splitting of the hetero¬ 
typic chromosomes until after the transverse splitting occurs. 
The longitudinal splitting was visible just before the chromosomes 
reached the poles. 
Gates (7) in his paper on Oenothera rubrinervis, states that the 
contraction of the chromatin material is synapsis and that since 
the cytoplasm of the cells shows no contraction, the cell is per¬ 
fectly fixed. For this reason, the contraction, so constantly 
observed at an early stage in the process, is not an artifact, but 
is a real contraction stage, leading to synapsis. As this contrac¬ 
tion proceeds the reticulm is re-arranged into a long, continuous 
delicate thread. No indication of a doubling or pairing of the 
threads was evident. After the synapsis the spirem shortens 
and thickens and begins to arrange itself more loosely in the 
nuclear cavity. This shortening is progressive and continues for 
some time. He states that the shortening may be uniform, or it 
may vary or may be irregularly constricted at varying intervals. 
This thickened thread now segments transversely into fourteen 
chromosomes—fourteen being the sporophytic number. Then 
these chromosomes break up into pairs which later fuse with each 
other leaving the x number of chromosomes. They are taken on 
the spindle and reduction follows in the usual way. 
In his paper on Oenothera lata x O. gigas (9) he begins his 
dicussion with the telophase The usual number of chromosomes 
found in the hybrid is twenty-one, seven being of maternal and 
fourteen of paternal origin. In the reduction one germ cell 
receives ten and the other eleven chromosomes. In a few cases 
nine and twelve chromosomes were the numbers found at the 
respective poles. One cell was found which had twenty chromo¬ 
somes, ten of which went to each pole. The segmentation into 
ten and eleven proves that there is not a pairing of homologus 
chromosomes of maternal and paternal origin but the segmenta¬ 
tion tends to be into two numerically equal parts. Gates claims 
evidence from his work, that there are two general methods of 
chromosome reduction, one a side to side pairing of chromatin 
threads (parasynapsis) to form a double spirem; the other involving 
an end to end arrangement (telosynapsis) of maternal and paternal 
chromosomes, to form a single spirem which afterwards splits 
longitudinally. He says an individual always has as many 
chromosomes as the sum of the chromosomes in the germ cells 
which go to form the new plant. This fact, he says, supports 
the genetic continuity of the chromosomes. He has not shown 
whether the chromosomes have equal or unequal hereditary 
value. 
